Scalable sparse matrix multiply acceleration using systolic arrays with feedback inputs

ABSTRACT

Described herein is a graphics processor including a plurality of processing clusters coupled with a host interface, each processing cluster comprising a plurality of multiprocessors, the plurality of multiprocessors interconnected via a data interconnect, and each multiprocessor comprising sparse matrix multiply acceleration hardware including a systolic processing array with feedback inputs.

CROSS-REFERENCE

This present application is a continuation application of U.S.application Ser. No. 17/527,882, filed Nov. 16, 2021, which is acontinuation of U.S. Pat. No. 11,204,977, issued on Dec. 21, 2021, whichclaims priority to India provisional patent application number202041019059, filed on May 5, 2020, which is hereby incorporated hereinby reference.

BACKGROUND

Systolic matrix multiplication used in machine learning workloads have asignificant percentage of zeros (sparse-data workloads). Multiplicationof these zeros can be skipped and thus, overall performance improved.Current systolic architectures may provide support for sparsity withinworkloads, but such architectures may not gracefully scale.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the features of the present embodiments canbe understood in detail, a more particular description of theembodiments may be had by reference to the detailed description belowand the appended drawings. It is to be noted, however, that the appendeddrawings illustrate only typical embodiments and are therefore not to beconsidered limiting of its scope.

FIG. 1 is a block diagram of a processing system, according to anembodiment;

FIG. 2A-2D illustrate computing systems and graphics processors providedby embodiments described herein;

FIG. 3A-3C illustrate block diagrams of additional graphics processorand compute accelerator architectures provided by embodiments describedherein;

FIG. 4 is a block diagram of a graphics processing engine of a graphicsprocessor in accordance with some embodiments;

FIG. 5A-5B illustrate thread execution logic including an array ofprocessing elements employed in a graphics processor core according toembodiments described herein;

FIG. 6 illustrates an additional execution unit, according to anembodiment;

FIG. 7 is a block diagram illustrating graphics processor instructionformats according to some embodiments;

FIG. 8 is a block diagram of a graphics processor according to anotherembodiment;

FIG. 9A-9B illustrate a graphics processor command format and commandsequence, according to some embodiments;

FIG. 10 illustrates exemplary graphics software architecture for a dataprocessing system according to some embodiments;

FIG. 11A is a block diagram illustrating an IP core development system,according to an embodiment;

FIG. 11B illustrates a cross-section side view of an integrated circuitpackage assembly, according to some embodiments described herein;

FIG. 11C illustrates a package assembly that includes multiple units ofhardware logic chiplets connected to a substrate;

FIG. 11D illustrates a package assembly including interchangeablechiplets, according to an embodiment;

FIG. 12 is a block diagram illustrating an exemplary system on a chipintegrated circuit that may be fabricated using one or more IP cores,according to an embodiment;

FIG. 13A-13B are block diagrams illustrating exemplary graphicsprocessors for use within an SoC, according to embodiments describedherein;

FIG. 14 is a block diagram of a data processing system, according to anembodiment;

FIG. 15 illustrates a matrix operation performed by an instructionpipeline, according to an embodiment;

FIG. 16 illustrates a systolic array of multiplier/adder circuitsorganized in a pipelined fashion;

FIG. 17A-17B illustrates the use of a four-deep systolic array tocompute an equivalent array of eight systolic stages;

FIG. 18A-18B show time diagrams of systolic architectures;

FIG. 19 illustrates a two path Matrix Multiply accelerator on which eachpath has a depth of four stages;

FIG. 20 illustrates a four path Matrix Multiply accelerator on whicheach path has a depth of two stages.

FIG. 21 illustrates a scalable sparse matrix multiply accelerator usingsystolic arrays with feedback inputs;

FIG. 22 illustrates Src2 inputs including sparse data;

FIG. 23 illustrates a scalable sparse matrix multiply accelerator usingsystolic arrays with feedback inputs and outputs on each stage;

FIG. 24 illustrates a method of performing operations on a scalablesparse matrix multiply accelerator described herein;

FIG. 25 illustrates a method of performing a matrix multiply operationusing a sparse Src2 input matrix; and

FIG. 26 is a block diagram of a computing device including a graphicsprocessor, according to an embodiment.

DETAILED DESCRIPTION

Described herein are devices, systems, and methods to enable scalablesparse matrix multiply acceleration using systolic arrays with feedbackinputs.

For the purposes of explanation, numerous specific details are set forthto provide a thorough understanding of the various embodiments describedbelow. However, it will be apparent to a skilled practitioner in the artthat the embodiments may be practiced without some of these specificdetails. In other instances, well-known structures and devices are shownin block diagram form to avoid obscuring the underlying principles, andto provide a more thorough understanding of embodiments. Although someof the following embodiments are described with reference to a graphicsprocessor, the techniques and teachings described herein may be appliedto various types of circuits or semiconductor devices, including generalpurpose processing devices or graphic processing devices. Referenceherein to “one embodiment” or “an embodiment” indicate that a particularfeature, structure, or characteristic described in connection orassociation with the embodiment can be included in at least one of suchembodiments. However, the appearances of the phrase “in one embodiment”in various places in the specification do not necessarily all refer tothe same embodiment.

In the following description and claims, the terms “coupled” and“connected,” along with their derivatives, may be used. It should beunderstood that these terms are not intended as synonyms for each other.“Coupled” is used to indicate that two or more elements, which may ormay not be in direct physical or electrical contact with each other,co-operate or interact with each other. “Connected” is used to indicatethe establishment of communication between two or more elements that arecoupled with each other.

In the description that follows, FIGS. 1 through 13A-13B provide anoverview of exemplary data processing system and graphics processorlogic that incorporates or relates to the various embodiments. FIGS.14-26 provide specific details of the various embodiments. Some aspectsof the following embodiments are described with reference to a graphicsprocessor, while other aspects are described with respect to ageneral-purpose processor, such as a central processing unit (CPU).Similar techniques and teachings can be applied to other types ofcircuits or semiconductor devices, including but not limited to a manyintegrated core processor, a GPU cluster, or one or more instances of afield programmable gate array (FPGA). In general, the teachings areapplicable to any processor or machine that manipulates or processesimage (e.g., sample, pixel), vertex data, or geometry data or thatperforms parallel processing operations for machine learning andhigh-performance computing applications.

System Overview

FIG. 1 is a block diagram of a processing system 100, according to anembodiment. System 100 may be used in a single processor desktop system,a multiprocessor workstation system, or a server system having a largenumber of processors 102 or processor cores 107. In one embodiment, thesystem 100 is a processing platform incorporated within asystem-on-a-chip (SoC) integrated circuit for use in mobile, handheld,or embedded devices such as within Internet-of-things (IoT) devices withwired or wireless connectivity to a local or wide area network.

In one embodiment, system 100 can include, couple with, or be integratedwithin: a server-based gaming platform; a game console, including a gameand media console; a mobile gaming console, a handheld game console, oran online game console. In some embodiments the system 100 is part of amobile phone, smart phone, tablet computing device or mobileInternet-connected device such as a laptop with low internal storagecapacity. Processing system 100 can also include, couple with, or beintegrated within: a wearable device, such as a smart watch wearabledevice; smart eyewear or clothing enhanced with augmented reality (AR)or virtual reality (VR) features to provide visual, audio or tactileoutputs to supplement real world visual, audio or tactile experiences orotherwise provide text, audio, graphics, video, holographic images orvideo, or tactile feedback; other augmented reality (AR) device; orother virtual reality (VR) device. In some embodiments, the processingsystem 100 includes or is part of a television or set top box device. Inone embodiment, system 100 can include, couple with, or be integratedwithin a self-driving vehicle such as a bus, tractor trailer, car, motoror electric power cycle, plane or glider (or any combination thereof).The self-driving vehicle may use system 100 to process the environmentsensed around the vehicle.

In some embodiments, the one or more processors 102 each include one ormore processor cores 107 to process instructions which, when executed,perform operations for system or user software. In some embodiments, atleast one of the one or more processor cores 107 is configured toprocess a specific instruction set 109. In some embodiments, instructionset 109 may facilitate Complex Instruction Set Computing (CISC), ReducedInstruction Set Computing (RISC), or computing via a Very LongInstruction Word (VLIW). One or more processor cores 107 may process adifferent instruction set 109, which may include instructions tofacilitate the emulation of other instruction sets. Processor core 107may also include other processing devices, such as a Digital SignalProcessor (DSP).

In some embodiments, the processor 102 includes cache memory 104.Depending on the architecture, the processor 102 can have a singleinternal cache or multiple levels of internal cache. In someembodiments, the cache memory is shared among various components of theprocessor 102. In some embodiments, the processor 102 also uses anexternal cache (e.g., a Level-3 (L3) cache or Last Level Cache (LLC))(not shown), which may be shared among processor cores 107 using knowncache coherency techniques. A register file 106 can be additionallyincluded in processor 102 and may include different types of registersfor storing different types of data (e.g., integer registers, floatingpoint registers, status registers, and an instruction pointer register).Some registers may be general-purpose registers, while other registersmay be specific to the design of the processor 102.

In some embodiments, one or more processor(s) 102 are coupled with oneor more interface bus(es) 110 to transmit communication signals such asaddress, data, or control signals between processor 102 and othercomponents in the system 100. The interface bus 110, in one embodiment,can be a processor bus, such as a version of the Direct Media Interface(DMI) bus. However, processor busses are not limited to the DMI bus, andmay include one or more Peripheral Component Interconnect buses (e.g.,PCI, PCI express), memory busses, or other types of interface busses. Inone embodiment the processor(s) 102 include an integrated memorycontroller 116 and a platform controller hub 130. The memory controller116 facilitates communication between a memory device and othercomponents of the system 100, while the platform controller hub (PCH)130 provides connections to I/O devices via a local I/O bus.

The memory device 120 can be a dynamic random-access memory (DRAM)device, a static random-access memory (SRAM) device, flash memorydevice, phase-change memory device, or some other memory device havingsuitable performance to serve as process memory. In one embodiment thememory device 120 can operate as system memory for the system 100, tostore data 122 and instructions 121 for use when the one or moreprocessors 102 executes an application or process. Memory controller 116also couples with an optional external graphics processor 118, which maycommunicate with the one or more graphics processors 108 in processors102 to perform graphics and media operations. In some embodiments,graphics, media, and or compute operations may be assisted by anaccelerator 112 which is a coprocessor that can be configured to performa specialized set of graphics, media, or compute operations. Forexample, in one embodiment the accelerator 112 is a matrixmultiplication accelerator used to optimize machine learning or computeoperations. In one embodiment the accelerator 112 is a ray-tracingaccelerator that can be used to perform ray-tracing operations inconcert with the graphics processor 108. In one embodiment, an externalaccelerator 119 may be used in place of or in concert with theaccelerator 112.

In some embodiments a display device 111 can connect to the processor(s)102. The display device 111 can be one or more of an internal displaydevice, as in a mobile electronic device or a laptop device or anexternal display device attached via a display interface (e.g.,DisplayPort, etc.). In one embodiment the display device 111 can be ahead mounted display (HMD) such as a stereoscopic display device for usein virtual reality (VR) applications or augmented reality (AR)applications.

In some embodiments the platform controller hub 130 enables peripheralsto connect to memory device 120 and processor 102 via a high-speed I/Obus. The I/O peripherals include, but are not limited to, an audiocontroller 146, a network controller 134, a firmware interface 128, awireless transceiver 126, touch sensors 125, a data storage device 124(e.g., non-volatile memory, volatile memory, hard disk drive, flashmemory, NAND, 3D NAND, 3D XPoint, etc.). The data storage device 124 canconnect via a storage interface (e.g., SATA) or via a peripheral bus,such as a Peripheral Component Interconnect bus (e.g., PCI, PCIexpress). The touch sensors 125 can include touch screen sensors,pressure sensors, or fingerprint sensors. The wireless transceiver 126can be a Wi-Fi transceiver, a Bluetooth transceiver, or a mobile networktransceiver such as a 3G, 4G, 5G, or Long-Term Evolution (LTE)transceiver. The firmware interface 128 enables communication withsystem firmware, and can be, for example, a unified extensible firmwareinterface (UEFI). The network controller 134 can enable a networkconnection to a wired network. In some embodiments, a high-performancenetwork controller (not shown) couples with the interface bus 110. Theaudio controller 146, in one embodiment, is a multi-channel highdefinition audio controller. In one embodiment the system 100 includesan optional legacy I/O controller 140 for coupling legacy (e.g.,Personal System 2 (PS/2)) devices to the system. The platform controllerhub 130 can also connect to one or more Universal Serial Bus (USB)controllers 142 connect input devices, such as keyboard and mouse 143combinations, a camera 144, or other USB input devices.

It will be appreciated that the system 100 shown is exemplary and notlimiting, as other types of data processing systems that are differentlyconfigured may also be used. For example, an instance of the memorycontroller 116 and platform controller hub 130 may be integrated into adiscreet external graphics processor, such as the external graphicsprocessor 118. In one embodiment the platform controller hub 130 and/ormemory controller 116 may be external to the one or more processor(s)102. For example, the system 100 can include an external memorycontroller 116 and platform controller hub 130, which may be configuredas a memory controller hub and peripheral controller hub within a systemchipset that is in communication with the processor(s) 102.

For example, circuit boards (“sleds”) can be used on which componentssuch as CPUs, memory, and other components are placed are designed forincreased thermal performance. In some examples, processing componentssuch as the processors are located on a top side of a sled while nearmemory, such as DIMMs, are located on a bottom side of the sled. As aresult of the enhanced airflow provided by this design, the componentsmay operate at higher frequencies and power levels than in typicalsystems, thereby increasing performance. Furthermore, the sleds areconfigured to blindly mate with power and data communication cables in arack, thereby enhancing their ability to be quickly removed, upgraded,reinstalled, and/or replaced. Similarly, individual components locatedon the sleds, such as processors, accelerators, memory, and data storagedrives, are configured to be easily upgraded due to their increasedspacing from each other. In the illustrative embodiment, the componentsadditionally include hardware attestation features to prove theirauthenticity.

A data center can utilize a single network architecture (“fabric”) thatsupports multiple other network architectures including Ethernet andOmni-Path. The sleds can be coupled to switches via optical fibers,which provide higher bandwidth and lower latency than typical twistedpair cabling (e.g., Category 5, Category 5e, Category 6, etc.). Due tothe high bandwidth, low latency interconnections and networkarchitecture, the data center may, in use, pool resources, such asmemory, accelerators (e.g., GPUs, graphics accelerators, FPGAs, ASICs,neural network and/or artificial intelligence accelerators, etc.), anddata storage drives that are physically disaggregated, and provide themto compute resources (e.g., processors) on an as needed basis, enablingthe compute resources to access the pooled resources as if they werelocal.

A power supply or source can provide voltage and/or current to system100 or any component or system described herein. In one example, thepower supply includes an AC to DC (alternating current to directcurrent) adapter to plug into a wall outlet. Such AC power can berenewable energy (e.g., solar power) power source. In one example, powersource includes a DC power source, such as an external AC to DCconverter. In one example, power source or power supply includeswireless charging hardware to charge via proximity to a charging field.In one example, power source can include an internal battery,alternating current supply, motion-based power supply, solar powersupply, or fuel cell source.

FIG. 2A-2D illustrate computing systems and graphics processors providedby embodiments described herein. The elements of FIG. 2A-2D having thesame reference numbers (or names) as the elements of any other figureherein can operate or function in any manner similar to that describedelsewhere herein, but are not limited to such.

FIG. 2A is a block diagram of an embodiment of a processor 200 havingone or more processor cores 202A-202N, an integrated memory controller214, and an integrated graphics processor 208. Processor 200 can includeadditional cores up to and including additional core 202N represented bythe dashed lined boxes. Each of processor cores 202A-202N includes oneor more internal cache units 204A-204N. In some embodiments eachprocessor core also has access to one or more shared cached units 206.The internal cache units 204A-204N and shared cache units 206 representa cache memory hierarchy within the processor 200. The cache memoryhierarchy may include at least one level of instruction and data cachewithin each processor core and one or more levels of shared mid-levelcache, such as a Level 2 (L2), Level 3 (L3), Level 4 (L4), or otherlevels of cache, where the highest level of cache before external memoryis classified as the LLC. In some embodiments, cache coherency logicmaintains coherency between the various cache units 206 and 204A-204N.

In some embodiments, processor 200 may also include a set of one or morebus controller units 216 and a system agent core 210. The one or morebus controller units 216 manage a set of peripheral buses, such as oneor more PCI or PCI express busses. System agent core 210 providesmanagement functionality for the various processor components. In someembodiments, system agent core 210 includes one or more integratedmemory controllers 214 to manage access to various external memorydevices (not shown).

In some embodiments, one or more of the processor cores 202A-202Ninclude support for simultaneous multi-threading. In such embodiment,the system agent core 210 includes components for coordinating andoperating cores 202A-202N during multi-threaded processing. System agentcore 210 may additionally include a power control unit (PCU), whichincludes logic and components to regulate the power state of processorcores 202A-202N and graphics processor 208.

In some embodiments, processor 200 additionally includes graphicsprocessor 208 to execute graphics processing operations. In someembodiments, the graphics processor 208 couples with the set of sharedcache units 206, and the system agent core 210, including the one ormore integrated memory controllers 214. In some embodiments, the systemagent core 210 also includes a display controller 211 to drive graphicsprocessor output to one or more coupled displays. In some embodiments,display controller 211 may also be a separate module coupled with thegraphics processor via at least one interconnect, or may be integratedwithin the graphics processor 208.

In some embodiments, a ring-based interconnect 212 is used to couple theinternal components of the processor 200. However, an alternativeinterconnect unit may be used, such as a point-to-point interconnect, aswitched interconnect, or other techniques, including techniques wellknown in the art. In some embodiments, graphics processor 208 coupleswith the ring-based interconnect 212 via an I/O link 213.

The exemplary I/O link 213 represents at least one of multiple varietiesof I/O interconnects, including an on package I/O interconnect whichfacilitates communication between various processor components and ahigh-performance embedded memory module 218, such as an eDRAM module. Insome embodiments, each of the processor cores 202A-202N and graphicsprocessor 208 can use embedded memory modules 218 as a shared Last LevelCache.

In some embodiments, processor cores 202A-202N are homogenous coresexecuting the same instruction set architecture. In another embodiment,processor cores 202A-202N are heterogeneous in terms of instruction setarchitecture (ISA), where one or more of processor cores 202A-202Nexecute a first instruction set, while at least one of the other coresexecutes a subset of the first instruction set or a differentinstruction set. In one embodiment, processor cores 202A-202N areheterogeneous in terms of microarchitecture, where one or more coreshaving a relatively higher power consumption couple with one or morepower cores having a lower power consumption. In one embodiment,processor cores 202A-202N are heterogeneous in terms of computationalcapability. Additionally, processor 200 can be implemented on one ormore chips or as an SoC integrated circuit having the illustratedcomponents, in addition to other components.

FIG. 2B is a block diagram of hardware logic of a graphics processorcore 219, according to some embodiments described herein. Elements ofFIG. 2B having the same reference numbers (or names) as the elements ofany other figure herein can operate or function in any manner similar tothat described elsewhere herein, but are not limited to such. Thegraphics processor core 219, sometimes referred to as a core slice, canbe one or multiple graphics cores within a modular graphics processor.The graphics processor core 219 is exemplary of one graphics core slice,and a graphics processor as described herein may include multiplegraphics core slices based on target power and performance envelopes.Each graphics processor core 219 can include a fixed function block 230coupled with multiple sub-cores 221A-221F, also referred to assub-slices, that include modular blocks of general-purpose and fixedfunction logic.

In some embodiments, the fixed function block 230 includes ageometry/fixed function pipeline 231 that can be shared by all sub-coresin the graphics processor core 219, for example, in lower performanceand/or lower power graphics processor implementations. In variousembodiments, the geometry/fixed function pipeline 231 includes a 3Dfixed function pipeline (e.g., 3D pipeline 312 as in FIG. 3A and FIG. 4, described below) a video front-end unit, a thread spawner and threaddispatcher, and a unified return buffer manager, which manages unifiedreturn buffers (e.g., unified return buffer 418 in FIG. 4 , as describedbelow).

In one embodiment the fixed function block 230 also includes a graphicsSoC interface 232, a graphics microcontroller 233, and a media pipeline234. The graphics SoC interface 232 provides an interface between thegraphics processor core 219 and other processor cores within a system ona chip integrated circuit. The graphics microcontroller 233 is aprogrammable sub-processor that is configurable to manage variousfunctions of the graphics processor core 219, including thread dispatch,scheduling, and pre-emption. The media pipeline 234 (e.g., mediapipeline 316 of FIG. 3A and FIG. 4 ) includes logic to facilitate thedecoding, encoding, pre-processing, and/or post-processing of multimediadata, including image and video data. The media pipeline 234 implementmedia operations via requests to compute or sampling logic within thesub-cores 221-221F.

In one embodiment the SoC interface 232 enables the graphics processorcore 219 to communicate with general-purpose application processor cores(e.g., CPUs) and/or other components within an SoC, including memoryhierarchy elements such as a shared last level cache memory, the systemRAM, and/or embedded on-chip or on-package DRAM. The SoC interface 232can also enable communication with fixed function devices within theSoC, such as camera imaging pipelines, and enables the use of and/orimplements global memory atomics that may be shared between the graphicsprocessor core 219 and CPUs within the SoC. The SoC interface 232 canalso implement power management controls for the graphics processor core219 and enable an interface between a clock domain of the graphics core219 and other clock domains within the SoC. In one embodiment the SoCinterface 232 enables receipt of command buffers from a command streamerand global thread dispatcher that are configured to provide commands andinstructions to each of one or more graphics cores within a graphicsprocessor. The commands and instructions can be dispatched to the mediapipeline 234, when media operations are to be performed, or a geometryand fixed function pipeline (e.g., geometry and fixed function pipeline231, geometry and fixed function pipeline 237) when graphics processingoperations are to be performed.

The graphics microcontroller 233 can be configured to perform variousscheduling and management tasks for the graphics processor core 219. Inone embodiment the graphics microcontroller 233 can perform graphicsand/or compute workload scheduling on the various graphics parallelengines within execution unit (EU) arrays 222A-222F, 224A-224F withinthe sub-cores 221A-221F. In this scheduling model, host softwareexecuting on a CPU core of an SoC including the graphics processor core219 can submit workloads one of multiple graphic processor doorbells,which invokes a scheduling operation on the appropriate graphics engine.Scheduling operations include determining which workload to run next,submitting a workload to a command streamer, pre-empting existingworkloads running on an engine, monitoring progress of a workload, andnotifying host software when a workload is complete. In one embodimentthe graphics microcontroller 233 can also facilitate low-power or idlestates for the graphics processor core 219, providing the graphicsprocessor core 219 with the ability to save and restore registers withinthe graphics processor core 219 across low-power state transitionsindependently from the operating system and/or graphics driver softwareon the system.

The graphics processor core 219 may have greater than or fewer than theillustrated sub-cores 221A-221F, up to N modular sub-cores. For each setof N sub-cores, the graphics processor core 219 can also include sharedfunction logic 235, shared and/or cache memory 236, a geometry/fixedfunction pipeline 237, as well as additional fixed function logic 238 toaccelerate various graphics and compute processing operations. Theshared function logic 235 can include logic units associated with theshared function logic 420 of FIG. 4 (e.g., sampler, math, and/orinter-thread communication logic) that can be shared by each N sub-coreswithin the graphics processor core 219. The shared and/or cache memory236 can be a last-level cache for the set of N sub-cores 221A-221Fwithin the graphics processor core 219, and can also serve as sharedmemory that is accessible by multiple sub-cores. The geometry/fixedfunction pipeline 237 can be included instead of the geometry/fixedfunction pipeline 231 within the fixed function block 230 and caninclude the same or similar logic units.

In one embodiment the graphics processor core 219 includes additionalfixed function logic 238 that can include various fixed functionacceleration logic for use by the graphics processor core 219. In oneembodiment the additional fixed function logic 238 includes anadditional geometry pipeline for use in position only shading. Inposition-only shading, two geometry pipelines exist, the full geometrypipeline within the geometry/fixed function pipeline 238, 231, and acull pipeline, which is an additional geometry pipeline which may beincluded within the additional fixed function logic 238. In oneembodiment the cull pipeline is a trimmed down version of the fullgeometry pipeline. The full pipeline and the cull pipeline can executedifferent instances of the same application, each instance having aseparate context. Position only shading can hide long cull runs ofdiscarded triangles, enabling shading to be completed earlier in someinstances. For example and in one embodiment the cull pipeline logicwithin the additional fixed function logic 238 can execute positionshaders in parallel with the main application and generally generatescritical results faster than the full pipeline, as the cull pipelinefetches and shades only the position attribute of the vertices, withoutperforming rasterization and rendering of the pixels to the framebuffer. The cull pipeline can use the generated critical results tocompute visibility information for all the triangles without regard towhether those triangles are culled. The full pipeline (which in thisinstance may be referred to as a replay pipeline) can consume thevisibility information to skip the culled triangles to shade only thevisible triangles that are finally passed to the rasterization phase.

In one embodiment the additional fixed function logic 238 can alsoinclude machine-learning acceleration logic, such as fixed functionmatrix multiplication logic, for implementations including optimizationsfor machine learning training or inferencing.

Within each graphics sub-core 221A-221F includes a set of executionresources that may be used to perform graphics, media, and computeoperations in response to requests by graphics pipeline, media pipeline,or shader programs. The graphics sub-cores 221A-221F include multiple EUarrays 222A-222F, 224A-224F, thread dispatch and inter-threadcommunication (TD/IC) logic 223A-223F, a 3D (e.g., texture) sampler225A-225F, a media sampler 226A-226F, a shader processor 227A-227F, andshared local memory (SLM) 228A-228F. The EU arrays 222A-222F, 224A-224Feach include multiple execution units, which are general-purposegraphics processing units capable of performing floating-point andinteger/fixed-point logic operations in service of a graphics, media, orcompute operation, including graphics, media, or compute shaderprograms. The TD/IC logic 223A-223F performs local thread dispatch andthread control operations for the execution units within a sub-core andfacilitate communication between threads executing on the executionunits of the sub-core. The 3D sampler 225A-225F can read texture orother 3D graphics related data into memory. The 3D sampler can readtexture data differently based on a configured sample state and thetexture format associated with a given texture. The media sampler226A-226F can perform similar read operations based on the type andformat associated with media data. In one embodiment, each graphicssub-core 221A-221F can alternately include a unified 3D and mediasampler. Threads executing on the execution units within each of thesub-cores 221A-221F can make use of shared local memory 228A-228F withineach sub-core, to enable threads executing within a thread group toexecute using a common pool of on-chip memory.

FIG. 2C illustrates a graphics processing unit (GPU) 239 that includesdedicated sets of graphics processing resources arranged into multi-coregroups 240A-240N. While the details of only a single multi-core group240A are provided, it will be appreciated that the other multi-coregroups 240B-240N may be equipped with the same or similar sets ofgraphics processing resources.

As illustrated, a multi-core group 240A may include a set of graphicscores 243, a set of tensor cores 244, and a set of ray tracing cores245. A scheduler/dispatcher 241 schedules and dispatches the graphicsthreads for execution on the various cores 243, 244, 245. A set ofregister files 242 store operand values used by the cores 243, 244, 245when executing the graphics threads. These may include, for example,integer registers for storing integer values, floating point registersfor storing floating point values, vector registers for storing packeddata elements (integer and/or floating-point data elements) and tileregisters for storing tensor/matrix values. In one embodiment, the tileregisters are implemented as combined sets of vector registers.

One or more combined level 1 (L1) caches and shared memory units 247store graphics data such as texture data, vertex data, pixel data, raydata, bounding volume data, etc., locally within each multi-core group240A. One or more texture units 247 can also be used to performtexturing operations, such as texture mapping and sampling. A Level 2(L2) cache 253 shared by all or a subset of the multi-core groups240A-240N stores graphics data and/or instructions for multipleconcurrent graphics threads. As illustrated, the L2 cache 253 may beshared across a plurality of multi-core groups 240A-240N. One or morememory controllers 248 couple the GPU 239 to a memory 249 which may be asystem memory (e.g., DRAM) and/or a dedicated graphics memory (e.g.,GDDR6 memory).

Input/output (I/O) circuitry 250 couples the GPU 239 to one or more I/Odevices 252 such as digital signal processors (DSPs), networkcontrollers, or user input devices. An on-chip interconnect may be usedto couple the I/O devices 252 to the GPU 239 and memory 249. One or moreI/O memory management units (IOMMUs) 251 of the I/O circuitry 250 couplethe I/O devices 252 directly to the system memory 249. In oneembodiment, the IOMMU 251 manages multiple sets of page tables to mapvirtual addresses to physical addresses in system memory 249. In thisembodiment, the I/O devices 252, CPU(s) 246, and GPU(s) 239 may sharethe same virtual address space.

In one implementation, the IOMMU 251 supports virtualization. In thiscase, it may manage a first set of page tables to map guest/graphicsvirtual addresses to guest/graphics physical addresses and a second setof page tables to map the guest/graphics physical addresses tosystem/host physical addresses (e.g., within system memory 249). Thebase addresses of each of the first and second sets of page tables maybe stored in control registers and swapped out on a context switch(e.g., so that the new context is provided with access to the relevantset of page tables). While not illustrated in FIG. 2C, each of the cores243, 244, 245 and/or multi-core groups 240A-240N may include translationlookaside buffers (TLBs) to cache guest virtual to guest physicaltranslations, guest physical to host physical translations, and guestvirtual to host physical translations.

In one embodiment, the CPU(s) 246, GPU(s) 239, and I/O devices 252 areintegrated on a single semiconductor chip and/or chip package. Theillustrated memory 249 may be integrated on the same chip or may becoupled to the memory controllers 248 via an off-chip interface. In oneimplementation, the memory 249 comprises GDDR6 memory which shares thesame virtual address space as other physical system-level memories,although the underlying principles of the invention are not limited tothis specific implementation.

In one embodiment, the tensor cores 244 include a plurality of executionunits specifically designed to perform matrix operations, which are thefundamental compute operation used to perform deep learning operations.For example, simultaneous matrix multiplication operations may be usedfor neural network training and inferencing. The tensor cores 244 mayperform matrix processing using a variety of operand precisionsincluding single precision floating-point (e.g., 32 bits),half-precision floating point (e.g., 16 bits), integer words (16 bits),bytes (8 bits), and half-bytes (4 bits). In one embodiment, a neuralnetwork implementation extracts features of each rendered scene,potentially combining details from multiple frames, to construct ahigh-quality final image.

In deep learning implementations, parallel matrix multiplication workmay be scheduled for execution on the tensor cores 244. The training ofneural networks, in particular, requires a significant number of matrixdot product operations. In order to process an inner-product formulationof an N×N×N matrix multiply, the tensor cores 244 may include at least Ndot-product processing elements. Before the matrix multiply begins, oneentire matrix is loaded into tile registers and at least one column of asecond matrix is loaded each cycle for N cycles. Each cycle, there are Ndot products that are processed.

Matrix elements may be stored at different precisions depending on theparticular implementation, including 16-bit words, 8-bit bytes (e.g.,INT8) and 4-bit half-bytes (e.g., INT4). Different precision modes maybe specified for the tensor cores 244 to ensure that the most efficientprecision is used for different workloads (e.g., such as inferencingworkloads which can tolerate quantization to bytes and half-bytes).

In one embodiment, the ray tracing cores 245 accelerate ray tracingoperations for both real-time ray tracing and non-real-time ray tracingimplementations. In particular, the ray tracing cores 245 include raytraversal/intersection circuitry for performing ray traversal usingbounding volume hierarchies (BVHs) and identifying intersections betweenrays and primitives enclosed within the BVH volumes. The ray tracingcores 245 may also include circuitry for performing depth testing andculling (e.g., using a Z buffer or similar arrangement). In oneimplementation, the ray tracing cores 245 perform traversal andintersection operations in concert with the image denoising techniquesdescribed herein, at least a portion of which may be executed on thetensor cores 244. For example, in one embodiment, the tensor cores 244implement a deep learning neural network to perform denoising of framesgenerated by the ray tracing cores 245. However, the CPU(s) 246,graphics cores 243, and/or ray tracing cores 245 may also implement allor a portion of the denoising and/or deep learning algorithms.

In addition, as described above, a distributed approach to denoising maybe employed in which the GPU 239 is in a computing device coupled toother computing devices over a network or high-speed interconnect. Inthis embodiment, the interconnected computing devices share neuralnetwork learning/training data to improve the speed with which theoverall system learns to perform denoising for different types of imageframes and/or different graphics applications.

In one embodiment, the ray tracing cores 245 process all BVH traversaland ray-primitive intersections, saving the graphics cores 243 frombeing overloaded with thousands of instructions per ray. In oneembodiment, each ray tracing core 245 includes a first set ofspecialized circuitry for performing bounding box tests (e.g., fortraversal operations) and a second set of specialized circuitry forperforming the ray-triangle intersection tests (e.g., intersecting rayswhich have been traversed). Thus, in one embodiment, the multi-coregroup 240A can simply launch a ray probe, and the ray tracing cores 245independently perform ray traversal and intersection and return hit data(e.g., a hit, no hit, multiple hits, etc.) to the thread context. Theother cores 243, 244 are freed to perform other graphics or compute workwhile the ray tracing cores 245 perform the traversal and intersectionoperations.

In one embodiment, each ray tracing core 245 includes a traversal unitto perform BVH testing operations and an intersection unit whichperforms ray-primitive intersection tests. The intersection unitgenerates a “hit”, “no hit”, or “multiple hit” response, which itprovides to the appropriate thread. During the traversal andintersection operations, the execution resources of the other cores(e.g., graphics cores 243 and tensor cores 244) are freed to performother forms of graphics work.

In one particular embodiment described below, a hybrid rasterization/raytracing approach is used in which work is distributed between thegraphics cores 243 and ray tracing cores 245.

In one embodiment, the ray tracing cores 245 (and/or other cores 243,244) include hardware support for a ray tracing instruction set such asMicrosoft's DirectX Ray Tracing (DXR) which includes a DispatchRayscommand, as well as ray-generation, closest-hit, any-hit, and missshaders, which enable the assignment of unique sets of shaders andtextures for each object. Another ray tracing platform which may besupported by the ray tracing cores 245, graphics cores 243 and tensorcores 244 is Vulkan 1.1.85. Note, however, that the underlyingprinciples of the invention are not limited to any particular raytracing ISA.

In general, the various cores 245, 244, 243 may support a ray tracinginstruction set that includes instructions/functions for ray generation,closest hit, any hit, ray-primitive intersection, per-primitive andhierarchical bounding box construction, miss, visit, and exceptions.More specifically, one embodiment includes ray tracing instructions toperform the following functions: Ray Generation—Ray generationinstructions may be executed for each pixel, sample, or otheruser-defined work assignment.

Closest Hit—A closest hit instruction may be executed to locate theclosest intersection point of a ray with primitives within a scene.

Any Hit—An any hit instruction identifies multiple intersections betweena ray and primitives within a scene, potentially to identify a newclosest intersection point.

Intersection—An intersection instruction performs a ray-primitiveintersection test and outputs a result.

Per-primitive Bounding box Construction—This instruction builds abounding box around a given primitive or group of primitives (e.g., whenbuilding a new BVH or other acceleration data structure).

Miss—Indicates that a ray misses all geometry within a scene, orspecified region of a scene.

Visit—Indicates the child volumes a ray will traverse.

Exceptions—Includes various types of exception handlers (e.g., invokedfor various error conditions).

FIG. 2D is a block diagram of general-purpose graphics processing unit(GPGPU) 270 that can be configured as a graphics processor and/orcompute accelerator, according to embodiments described herein. TheGPGPU 270 can interconnect with host processors (e.g., one or moreCPU(s) 246) and memory 271, 272 via one or more system and/or memorybusses. In one embodiment the memory 271 is system memory that may beshared with the one or more CPU(s) 246, while memory 272 is devicememory that is dedicated to the GPGPU 270. In one embodiment, componentswithin the GPGPU 270 and device memory 272 may be mapped into memoryaddresses that are accessible to the one or more CPU(s) 246. Access tomemory 271 and 272 may be facilitated via a memory controller 268. Inone embodiment the memory controller 268 includes an internal directmemory access (DMA) controller 269 or can include logic to performoperations that would otherwise be performed by a DMA controller.

The GPGPU 270 includes multiple cache memories, including an L2 cache253, L1 cache 254, an instruction cache 255, and shared memory 256, atleast a portion of which may also be partitioned as a cache memory. TheGPGPU 270 also includes multiple compute units 260A-260N. Each computeunit 260A-260N includes a set of vector registers 261, scalar registers262, vector logic units 263, and scalar logic units 264. The computeunits 260A-260N can also include local shared memory 265 and a programcounter 266. The compute units 260A-260N can couple with a constantcache 267, which can be used to store constant data, which is data thatwill not change during the run of kernel or shader program that executeson the GPGPU 270. In one embodiment the constant cache 267 is a scalardata cache and cached data can be fetched directly into the scalarregisters 262.

During operation, the one or more CPU(s) 246 can write commands intoregisters or memory in the GPGPU 270 that has been mapped into anaccessible address space. The command processors 257 can read thecommands from registers or memory and determine how those commands willbe processed within the GPGPU 270. A thread dispatcher 258 can then beused to dispatch threads to the compute units 260A-260N to perform thosecommands. Each compute unit 260A-260N can execute threads independentlyof the other compute units. Additionally, each compute unit 260A-260Ncan be independently configured for conditional computation and canconditionally output the results of computation to memory. The commandprocessors 257 can interrupt the one or more CPU(s) 246 when thesubmitted commands are complete.

FIG. 3A-3C illustrate block diagrams of additional graphics processorand compute accelerator architectures provided by embodiments describedherein. The elements of FIG. 3A-3C having the same reference numbers (ornames) as the elements of any other figure herein can operate orfunction in any manner similar to that described elsewhere herein, butare not limited to such.

FIG. 3A is a block diagram of a graphics processor 300, which may be adiscrete graphics processing unit, or may be a graphics processorintegrated with a plurality of processing cores, or other semiconductordevices such as, but not limited to, memory devices or networkinterfaces. In some embodiments, the graphics processor communicates viaa memory mapped I/O interface to registers on the graphics processor andwith commands placed into the processor memory. In some embodiments,graphics processor 300 includes a memory interface 314 to access memory.Memory interface 314 can be an interface to local memory, one or moreinternal caches, one or more shared external caches, and/or to systemmemory.

In some embodiments, graphics processor 300 also includes a displaycontroller 302 to drive display output data to a display device 318.Display controller 302 includes hardware for one or more overlay planesfor the display and composition of multiple layers of video or userinterface elements. The display device 318 can be an internal orexternal display device. In one embodiment the display device 318 is ahead mounted display device, such as a virtual reality (VR) displaydevice or an augmented reality (AR) display device. In some embodiments,graphics processor 300 includes a video codec engine 306 to encode,decode, or transcode media to, from, or between one or more mediaencoding formats, including, but not limited to Moving Picture ExpertsGroup (MPEG) formats such as MPEG-2, Advanced Video Coding (AVC) formatssuch as H.264/MPEG-4 AVC, H.265/HEVC, Alliance for Open Media (AOMedia)VP8, VP9, as well as the Society of Motion Picture & TelevisionEngineers (SMPTE) 421M/VC-1, and Joint Photographic Experts Group (JPEG)formats such as JPEG, and Motion JPEG (MJPEG) formats.

In some embodiments, graphics processor 300 includes a block imagetransfer (BLIT) engine 304 to perform two-dimensional (2D) rasterizeroperations including, for example, bit-boundary block transfers.However, in one embodiment, 2D graphics operations are performed usingone or more components of graphics processing engine (GPE) 310. In someembodiments, GPE 310 is a compute engine for performing graphicsoperations, including three-dimensional (3D) graphics operations andmedia operations.

In some embodiments, GPE 310 includes a 3D pipeline 312 for performing3D operations, such as rendering three-dimensional images and scenesusing processing functions that act upon 3D primitive shapes (e.g.,rectangle, triangle, etc.). The 3D pipeline 312 includes programmableand fixed function elements that perform various tasks within theelement and/or spawn execution threads to a 3D/Media sub-system 315.While 3D pipeline 312 can be used to perform media operations, anembodiment of GPE 310 also includes a media pipeline 316 that isspecifically used to perform media operations, such as videopost-processing and image enhancement.

In some embodiments, media pipeline 316 includes fixed function orprogrammable logic units to perform one or more specialized mediaoperations, such as video decode acceleration, video de-interlacing, andvideo encode acceleration in place of, or on behalf of video codecengine 306. In some embodiments, media pipeline 316 additionallyincludes a thread spawning unit to spawn threads for execution on3D/Media sub-system 315. The spawned threads perform computations forthe media operations on one or more graphics execution units included in3D/Media sub-system 315.

In some embodiments, 3D/Media subsystem 315 includes logic for executingthreads spawned by 3D pipeline 312 and media pipeline 316. In oneembodiment, the pipelines send thread execution requests to 3D/Mediasubsystem 315, which includes thread dispatch logic for arbitrating anddispatching the various requests to available thread executionresources. The execution resources include an array of graphicsexecution units to process the 3D and media threads. In someembodiments, 3D/Media subsystem 315 includes one or more internal cachesfor thread instructions and data. In some embodiments, the subsystemalso includes shared memory, including registers and addressable memory,to share data between threads and to store output data.

FIG. 3B illustrates a graphics processor 320 having a tiledarchitecture, according to embodiments described herein. In oneembodiment the graphics processor 320 includes a graphics processingengine cluster 322 having multiple instances of the graphics processingengine 310 of FIG. 3A within a graphics engine tile 310A-310D. Eachgraphics engine tile 310A-310D can be interconnected via a set of tileinterconnects 323A-323F. Each graphics engine tile 310A-310D can also beconnected to a memory module or memory device 326A-326D via memoryinterconnects 325A-325D. The memory devices 326A-326D can use anygraphics memory technology. For example, the memory devices 326A-326Dmay be graphics double data rate (GDDR) memory. The memory devices326A-326D, in one embodiment, are high-bandwidth memory (HBM) modulesthat can be on-die with their respective graphics engine tile 310A-310D.In one embodiment the memory devices 326A-326D are stacked memorydevices that can be stacked on top of their respective graphics enginetile 310A-310D. In one embodiment, each graphics engine tile 310A-310Dand associated memory 326A-326D reside on separate chiplets, which arebonded to a base die or base substrate, as described on further detailin FIG. 11B-11D.

The graphics processor 320 may be configured with a non-uniform memoryaccess (NUMA) system in which memory devices 326A-326D are coupled withassociated graphics engine tiles 310A-310D. A given memory device may beaccessed by graphics engine tiles other than the tile to which it isdirectly connected. However, access latency to the memory devices326A-326D may be lowest when accessing a local tile. In one embodiment,a cache coherent NUMA (ccNUMA) system is enabled that uses the tileinterconnects 323A-323F to enable communication between cachecontrollers within the graphics engine tiles 310A-310D to keep aconsistent memory image when more than one cache stores the same memorylocation.

The graphics processing engine cluster 322 can connect with an on-chipor on-package fabric interconnect 324. The fabric interconnect 324 canenable communication between graphics engine tiles 310A-310D andcomponents such as the video codec engine 306 and one or more copyengines 304. The copy engines 304 can be used to move data out of, into,and between the memory devices 326A-326D and memory that is external tothe graphics processor 320 (e.g., system memory). The fabricinterconnect 324 can also be used to interconnect the graphics enginetiles 310A-310D. The graphics processor 320 may optionally include adisplay controller 302 to enable a connection with an external displaydevice 318. The graphics processor may also be configured as a graphicsor compute accelerator. In the accelerator configuration, the displaycontroller 302 and display device 318 may be omitted.

The graphics processor 320 can connect to a host system via a hostinterface 328. The host interface 328 can enable communication betweenthe graphics processor 320, system memory, and/or other systemcomponents. The host interface 328 can be, for example a PCI express busor another type of host system interface.

FIG. 3C illustrates a compute accelerator 330, according to embodimentsdescribed herein. The compute accelerator 330 can include architecturalsimilarities with the graphics processor 320 of FIG. 3B and is optimizedfor compute acceleration. A compute engine cluster 332 can include a setof compute engine tiles 340A-340D that include execution logic that isoptimized for parallel or vector-based general-purpose computeoperations. In some embodiments, the compute engine tiles 340A-340D donot include fixed function graphics processing logic, although in oneembodiment one or more of the compute engine tiles 340A-340D can includelogic to perform media acceleration. The compute engine tiles 340A-340Dcan connect to memory 326A-326D via memory interconnects 325A-325D. Thememory 326A-326D and memory interconnects 325A-325D may be similartechnology as in graphics processor 320, or can be different. Thegraphics compute engine tiles 340A-340D can also be interconnected via aset of tile interconnects 323A-323F and may be connected with and/orinterconnected by a fabric interconnect 324. In one embodiment thecompute accelerator 330 includes a large L3 cache 336 that can beconfigured as a device-wide cache. The compute accelerator 330 can alsoconnect to a host processor and memory via a host interface 328 in asimilar manner as the graphics processor 320 of FIG. 3B.

Graphics Processing Engine

FIG. 4 is a block diagram of a graphics processing engine 410 of agraphics processor in accordance with some embodiments. In oneembodiment, the graphics processing engine (GPE) 410 is a version of theGPE 310 shown in FIG. 3A, and may also represent a graphics engine tile310A-310D of FIG. 3B. Elements of FIG. 4 having the same referencenumbers (or names) as the elements of any other figure herein canoperate or function in any manner similar to that described elsewhereherein, but are not limited to such. For example, the 3D pipeline 312and media pipeline 316 of FIG. 3A are illustrated. The media pipeline316 is optional in some embodiments of the GPE 410 and may not beexplicitly included within the GPE 410. For example, and in at least oneembodiment, a separate media and/or image processor is coupled to theGPE 410.

In some embodiments, GPE 410 couples with or includes a command streamer403, which provides a command stream to the 3D pipeline 312 and/or mediapipelines 316. In some embodiments, command streamer 403 is coupled withmemory, which can be system memory, or one or more of internal cachememory and shared cache memory. In some embodiments, command streamer403 receives commands from the memory and sends the commands to 3Dpipeline 312 and/or media pipeline 316. The commands are directivesfetched from a ring buffer, which stores commands for the 3D pipeline312 and media pipeline 316. In one embodiment, the ring buffer canadditionally include batch command buffers storing batches of multiplecommands. The commands for the 3D pipeline 312 can also includereferences to data stored in memory, such as but not limited to vertexand geometry data for the 3D pipeline 312 and/or image data and memoryobjects for the media pipeline 316. The 3D pipeline 312 and mediapipeline 316 process the commands and data by performing operations vialogic within the respective pipelines or by dispatching one or moreexecution threads to a graphics core array 414. In one embodiment thegraphics core array 414 include one or more blocks of graphics cores(e.g., graphics core(s) 415A, graphics core(s) 415B), each blockincluding one or more graphics cores. Each graphics core includes a setof graphics execution resources that includes general-purpose andgraphics specific execution logic to perform graphics and computeoperations, as well as fixed function texture processing and/or machinelearning and artificial intelligence acceleration logic.

In various embodiments the 3D pipeline 312 can include fixed functionand programmable logic to process one or more shader programs, such asvertex shaders, geometry shaders, pixel shaders, fragment shaders,compute shaders, or other shader programs, by processing theinstructions and dispatching execution threads to the graphics corearray 414. The graphics core array 414 provides a unified block ofexecution resources for use in processing these shader programs.Multi-purpose execution logic (e.g., execution units) within thegraphics core(s) 415A-414B of the graphics core array 414 includessupport for various 3D API shader languages and can execute multiplesimultaneous execution threads associated with multiple shaders.

In some embodiments, the graphics core array 414 includes executionlogic to perform media functions, such as video and/or image processing.In one embodiment, the execution units include general-purpose logicthat is programmable to perform parallel general-purpose computationaloperations, in addition to graphics processing operations. Thegeneral-purpose logic can perform processing operations in parallel orin conjunction with general-purpose logic within the processor core(s)107 of FIG. 1 or core 202A-202N as in FIG. 2A.

Output data generated by threads executing on the graphics core array414 can output data to memory in a unified return buffer (URB) 418. TheURB 418 can store data for multiple threads. In some embodiments the URB418 may be used to send data between different threads executing on thegraphics core array 414. In some embodiments the URB 418 mayadditionally be used for synchronization between threads on the graphicscore array and fixed function logic within the shared function logic420.

In some embodiments, graphics core array 414 is scalable, such that thearray includes a variable number of graphics cores, each having avariable number of execution units based on the target power andperformance level of GPE 410. In one embodiment the execution resourcesare dynamically scalable, such that execution resources may be enabledor disabled as needed.

The graphics core array 414 couples with shared function logic 420 thatincludes multiple resources that are shared between the graphics coresin the graphics core array. The shared functions within the sharedfunction logic 420 are hardware logic units that provide specializedsupplemental functionality to the graphics core array 414. In variousembodiments, shared function logic 420 includes but is not limited tosampler 421, math 422, and inter-thread communication (ITC) 423 logic.Additionally, some embodiments implement one or more cache(s) 425 withinthe shared function logic 420.

A shared function is implemented at least in a case where the demand fora given specialized function is insufficient for inclusion within thegraphics core array 414. Instead a single instantiation of thatspecialized function is implemented as a stand-alone entity in theshared function logic 420 and shared among the execution resourceswithin the graphics core array 414. The precise set of functions thatare shared between the graphics core array 414 and included within thegraphics core array 414 varies across embodiments. In some embodiments,specific shared functions within the shared function logic 420 that areused extensively by the graphics core array 414 may be included withinshared function logic 416 within the graphics core array 414. In variousembodiments, the shared function logic 416 within the graphics corearray 414 can include some or all logic within the shared function logic420. In one embodiment, all logic elements within the shared functionlogic 420 may be duplicated within the shared function logic 416 of thegraphics core array 414. In one embodiment the shared function logic 420is excluded in favor of the shared function logic 416 within thegraphics core array 414.

Execution Units

FIG. 5A-5B illustrate thread execution logic 500 including an array ofprocessing elements employed in a graphics processor core according toembodiments described herein. Elements of FIG. 5A-5B having the samereference numbers (or names) as the elements of any other figure hereincan operate or function in any manner similar to that describedelsewhere herein, but are not limited to such. FIG. 5A-5B illustrates anoverview of thread execution logic 500, which may be representative ofhardware logic illustrated with each sub-core 221A-221F of FIG. 2B. FIG.5A is representative of an execution unit within a general-purposegraphics processor, while FIG. 5B is representative of an execution unitthat may be used within a compute accelerator.

As illustrated in FIG. 5A, in some embodiments thread execution logic500 includes a shader processor 502, a thread dispatcher 504,instruction cache 506, a scalable execution unit array including aplurality of execution units 508A-508N, a sampler 510, shared localmemory 511, a data cache 512, and a data port 514. In one embodiment thescalable execution unit array can dynamically scale by enabling ordisabling one or more execution units (e.g., any of execution units508A, 508B, 508C, 508D, through 508N-1 and 508N) based on thecomputational requirements of a workload. In one embodiment the includedcomponents are interconnected via an interconnect fabric that links toeach of the components. In some embodiments, thread execution logic 500includes one or more connections to memory, such as system memory orcache memory, through one or more of instruction cache 506, data port514, sampler 510, and execution units 508A-508N. In some embodiments,each execution unit (e.g. 508A) is a stand-alone programmablegeneral-purpose computational unit that is capable of executing multiplesimultaneous hardware threads while processing multiple data elements inparallel for each thread. In various embodiments, the array of executionunits 508A-508N is scalable to include any number individual executionunits.

In some embodiments, the execution units 508A-508N are primarily used toexecute shader programs. A shader processor 502 can process the variousshader programs and dispatch execution threads associated with theshader programs via a thread dispatcher 504. In one embodiment thethread dispatcher includes logic to arbitrate thread initiation requestsfrom the graphics and media pipelines and instantiate the requestedthreads on one or more execution unit in the execution units 508A-508N.For example, a geometry pipeline can dispatch vertex, tessellation, orgeometry shaders to the thread execution logic for processing. In someembodiments, thread dispatcher 504 can also process runtime threadspawning requests from the executing shader programs.

In some embodiments, the execution units 508A-508N support aninstruction set that includes native support for many standard 3Dgraphics shader instructions, such that shader programs from graphicslibraries (e.g., Direct 3D and OpenGL) are executed with a minimaltranslation. The execution units support vertex and geometry processing(e.g., vertex programs, geometry programs, vertex shaders), pixelprocessing (e.g., pixel shaders, fragment shaders) and general-purposeprocessing (e.g., compute and media shaders). Each of the executionunits 508A-508N is capable of multi-issue single instruction multipledata (SIMD) execution and multi-threaded operation enables an efficientexecution environment in the face of higher latency memory accesses.Each hardware thread within each execution unit has a dedicatedhigh-bandwidth register file and associated independent thread-state.Execution is multi-issue per clock to pipelines capable of integer,single and double precision floating point operations, SIMD branchcapability, logical operations, transcendental operations, and othermiscellaneous operations. While waiting for data from memory or one ofthe shared functions, dependency logic within the execution units508A-508N causes a waiting thread to sleep until the requested data hasbeen returned. While the waiting thread is sleeping, hardware resourcesmay be devoted to processing other threads. For example, during a delayassociated with a vertex shader operation, an execution unit can performoperations for a pixel shader, fragment shader, or another type ofshader program, including a different vertex shader. Various embodimentscan apply to use execution by use of Single Instruction Multiple Thread(SIMT) as an alternate to use of SIMD or in addition to use of SIMD.Reference to a SIMD core or operation can apply also to SIMT or apply toSIMD in combination with SIMT.

Each execution unit in execution units 508A-508N operates on arrays ofdata elements. The number of data elements is the “execution size,” orthe number of channels for the instruction. An execution channel is alogical unit of execution for data element access, masking, and flowcontrol within instructions. The number of channels may be independentof the number of physical Arithmetic Logic Units (ALUs) orFloating-Point Units (FPUs) for a particular graphics processor. In someembodiments, execution units 508A-508N support integer andfloating-point data types.

The execution unit instruction set includes SIMD instructions. Thevarious data elements can be stored as a packed data type in a registerand the execution unit will process the various elements based on thedata size of the elements. For example, when operating on a 256-bit widevector, the 256 bits of the vector are stored in a register and theexecution unit operates on the vector as four separate 54-bit packeddata elements (Quad-Word (QW) size data elements), eight separate 32-bitpacked data elements (Double Word (DW) size data elements), sixteenseparate 16-bit packed data elements (Word (W) size data elements), orthirty-two separate 8-bit data elements (byte (B) size data elements).However, different vector widths and register sizes are possible.

In one embodiment one or more execution units can be combined into afused execution unit 509A-509N having thread control logic (507A-507N)that is common to the fused EUs. Multiple EUs can be fused into an EUgroup. Each EU in the fused EU group can be configured to execute aseparate SIMD hardware thread. The number of EUs in a fused EU group canvary according to embodiments. Additionally, various SIMD widths can beperformed per-EU, including but not limited to SIMD8, SIMD16, andSIMD32. Each fused graphics execution unit 509A-509N includes at leasttwo execution units. For example, fused execution unit 509A includes afirst EU 508A, second EU 508B, and thread control logic 507A that iscommon to the first EU 508A and the second EU 508B. The thread controllogic 507A controls threads executed on the fused graphics executionunit 509A, allowing each EU within the fused execution units 509A-509Nto execute using a common instruction pointer register.

One or more internal instruction caches (e.g., 506) are included in thethread execution logic 500 to cache thread instructions for theexecution units. In some embodiments, one or more data caches (e.g.,512) are included to cache thread data during thread execution. Threadsexecuting on the execution logic 500 can also store explicitly manageddata in the shared local memory 511. In some embodiments, a sampler 510is included to provide texture sampling for 3D operations and mediasampling for media operations. In some embodiments, sampler 510 includesspecialized texture or media sampling functionality to process textureor media data during the sampling process before providing the sampleddata to an execution unit.

During execution, the graphics and media pipelines send threadinitiation requests to thread execution logic 500 via thread spawningand dispatch logic. Once a group of geometric objects has been processedand rasterized into pixel data, pixel processor logic (e.g., pixelshader logic, fragment shader logic, etc.) within the shader processor502 is invoked to further compute output information and cause resultsto be written to output surfaces (e.g., color buffers, depth buffers,stencil buffers, etc.). In some embodiments, a pixel shader or fragmentshader calculates the values of the various vertex attributes that areto be interpolated across the rasterized object. In some embodiments,pixel processor logic within the shader processor 502 then executes anapplication programming interface (API)-supplied pixel or fragmentshader program. To execute the shader program, the shader processor 502dispatches threads to an execution unit (e.g., 508A) via threaddispatcher 504. In some embodiments, shader processor 502 uses texturesampling logic in the sampler 510 to access texture data in texture mapsstored in memory. Arithmetic operations on the texture data and theinput geometry data compute pixel color data for each geometricfragment, or discards one or more pixels from further processing.

In some embodiments, the data port 514 provides a memory accessmechanism for the thread execution logic 500 to output processed data tomemory for further processing on a graphics processor output pipeline.In some embodiments, the data port 514 includes or couples to one ormore cache memories (e.g., data cache 512) to cache data for memoryaccess via the data port.

In one embodiment, the execution logic 500 can also include a ray tracer505 that can provide ray tracing acceleration functionality. The raytracer 505 can support a ray tracing instruction set that includesinstructions/functions for ray generation. The ray tracing instructionset can be similar to or different from the ray-tracing instruction setsupported by the ray tracing cores 245 in FIG. 2C.

FIG. 5B illustrates exemplary internal details of an execution unit 508,according to embodiments. A graphics execution unit 508 can include aninstruction fetch unit 537, a general register file array (GRF) 524, anarchitectural register file array (ARF) 526, a thread arbiter 522, asend unit 530, a branch unit 532, a set of SIMD floating point units(FPUs) 534, and in one embodiment a set of dedicated integer SIMD ALUs535. The GRF 524 and ARF 526 includes the set of general register filesand architecture register files associated with each simultaneoushardware thread that may be active in the graphics execution unit 508.In one embodiment, per thread architectural state is maintained in theARF 526, while data used during thread execution is stored in the GRF524. The execution state of each thread, including the instructionpointers for each thread, can be held in thread-specific registers inthe ARF 526.

In one embodiment the graphics execution unit 508 has an architecturethat is a combination of Simultaneous Multi-Threading (SMT) andfine-grained Interleaved Multi-Threading (IMT). The architecture has amodular configuration that can be fine-tuned at design time based on atarget number of simultaneous threads and number of registers perexecution unit, where execution unit resources are divided across logicused to execute multiple simultaneous threads. The number of logicalthreads that may be executed by the graphics execution unit 508 is notlimited to the number of hardware threads, and multiple logical threadscan be assigned to each hardware thread.

In one embodiment, the graphics execution unit 508 can co-issue multipleinstructions, which may each be different instructions. The threadarbiter 522 of the graphics execution unit 508 can dispatch theinstructions to one of the send unit 530, branch unit 532, or SIMDFPU(s) 534 for execution. Each execution thread can access 128general-purpose registers within the GRF 524, where each register canstore 32 bytes, accessible as a SIMD 8-element vector of 32-bit dataelements. In one embodiment, each execution unit thread has access to 4Kbytes within the GRF 524, although embodiments are not so limited, andgreater or fewer register resources may be provided in otherembodiments. In one embodiment the graphics execution unit 508 ispartitioned into seven hardware threads that can independently performcomputational operations, although the number of threads per executionunit can also vary according to embodiments. For example, in oneembodiment up to 16 hardware threads are supported. In an embodiment inwhich seven threads may access 4 Kbytes, the GRF 524 can store a totalof 28 Kbytes. Where 16 threads may access 4 Kbytes, the GRF 524 canstore a total of 64 Kbytes. Flexible addressing modes can permitregisters to be addressed together to build effectively wider registersor to represent strided rectangular block data structures.

In one embodiment, memory operations, sampler operations, and otherlonger-latency system communications are dispatched via “send”instructions that are executed by the message passing send unit 530. Inone embodiment, branch instructions are dispatched to a dedicated branchunit 532 to facilitate SIMD divergence and eventual convergence.

In one embodiment the graphics execution unit 508 includes one or moreSIMD floating point units (FPU(s)) 534 to perform floating-pointoperations. In one embodiment, the FPU(s) 534 also support integercomputation. In one embodiment the FPU(s) 534 can SIMD execute up to Mnumber of 32-bit floating-point (or integer) operations, or SIMD executeup to 2M 16-bit integer or 16-bit floating-point operations. In oneembodiment, at least one of the FPU(s) provides extended math capabilityto support high-throughput transcendental math functions and doubleprecision 54-bit floating-point. In some embodiments, a set of 8-bitinteger SIMD ALUs 535 are also present, and may be specificallyoptimized to perform operations associated with machine learningcomputations.

In one embodiment, arrays of multiple instances of the graphicsexecution unit 508 can be instantiated in a graphics sub-core grouping(e.g., a sub-slice). For scalability, product architects can choose theexact number of execution units per sub-core grouping. In one embodimentthe execution unit 508 can execute instructions across a plurality ofexecution channels. In a further embodiment, each thread executed on thegraphics execution unit 508 is executed on a different channel.

FIG. 6 illustrates an additional execution unit 600, according to anembodiment. The execution unit 600 may be a compute-optimized executionunit for use in, for example, a compute engine tile 340A-340D as in FIG.3C, but is not limited as such. Variants of the execution unit 600 mayalso be used in a graphics engine tile 310A-310D as in FIG. 3B. In oneembodiment, the execution unit 600 includes a thread control unit 601, athread state unit 602, an instruction fetch/prefetch unit 603, and aninstruction decode unit 604. The execution unit 600 additionallyincludes a register file 606 that stores registers that can be assignedto hardware threads within the execution unit. The execution unit 600additionally includes a send unit 607 and a branch unit 608. In oneembodiment, the send unit 607 and branch unit 608 can operate similarlyas the send unit 530 and a branch unit 532 of the graphics executionunit 508 of FIG. 5B.

The execution unit 600 also includes a compute unit 610 that includesmultiple different types of functional units. In one embodiment thecompute unit 610 includes an ALU unit 611 that includes an array ofarithmetic logic units. The ALU unit 611 can be configured to perform64-bit, 32-bit, and 16-bit integer and floating-point operations.Integer and floating-point operations may be performed simultaneously.The compute unit 610 can also include a systolic array 612, and a mathunit 613. The systolic array 612 includes a W wide and D deep network ofdata processing units that can be used to perform vector or otherdata-parallel operations in a systolic manner. In one embodiment thesystolic array 612 can be configured to perform matrix operations, suchas matrix dot product operations. In one embodiment the systolic array612 support 16-bit floating point operations, as well as 8-bit and 4-bitinteger operations. In one embodiment the systolic array 612 can beconfigured to accelerate machine learning operations. In suchembodiments, the systolic array 612 can be configured with support forthe bfloat 16-bit floating point format. In one embodiment, a math unit613 can be included to perform a specific subset of mathematicaloperations in an efficient and lower-power manner than then ALU unit611. The math unit 613 can include a variant of math logic that may befound in shared function logic of a graphics processing engine providedby other embodiments (e.g., math logic 422 of the shared function logic420 of FIG. 4 ). In one embodiment the math unit 613 can be configuredto perform 32-bit and 64-bit floating point operations.

The thread control unit 601 includes logic to control the execution ofthreads within the execution unit. The thread control unit 601 caninclude thread arbitration logic to start, stop, and preempt executionof threads within the execution unit 600. The thread state unit 602 canbe used to store thread state for threads assigned to execute on theexecution unit 600. Storing the thread state within the execution unit600 enables the rapid pre-emption of threads when those threads becomeblocked or idle. The instruction fetch/prefetch unit 603 can fetchinstructions from an instruction cache of higher-level execution logic(e.g., instruction cache 506 as in FIG. 5A). The instructionfetch/prefetch unit 603 can also issue prefetch requests forinstructions to be loaded into the instruction cache based on ananalysis of currently executing threads. The instruction decode unit 604can be used to decode instructions to be executed by the compute units.In one embodiment, the instruction decode unit 604 can be used as asecondary decoder to decode complex instructions into constituentmicro-operations.

The execution unit 600 additionally includes a register file 606 thatcan be used by hardware threads executing on the execution unit 600.Registers in the register file 606 can be divided across the logic usedto execute multiple simultaneous threads within the compute unit 610 ofthe execution unit 600. The number of logical threads that may beexecuted by the graphics execution unit 600 is not limited to the numberof hardware threads, and multiple logical threads can be assigned toeach hardware thread. The size of the register file 606 can vary acrossembodiments based on the number of supported hardware threads. In oneembodiment, register renaming may be used to dynamically allocateregisters to hardware threads.

FIG. 7 is a block diagram illustrating graphics processor instructionformats 700 according to some embodiments. In one or more embodiment,the graphics processor execution units support an instruction set havinginstructions in multiple formats. The solid lined boxes illustrate thecomponents that are generally included in an execution unit instruction,while the dashed lines include components that are optional or that areonly included in a sub-set of the instructions. In some embodiments,instruction format 700 described and illustrated are macro-instructions,in that they are instructions supplied to the execution unit, as opposedto micro-operations resulting from instruction decode once theinstruction is processed.

In some embodiments, the graphics processor execution units nativelysupport instructions in a 128-bit instruction format 710. A 64-bitcompacted instruction format 730 is available for some instructionsbased on the selected instruction, instruction options, and number ofoperands. The native 128-bit instruction format 710 provides access toall instruction options, while some options and operations arerestricted in the 64-bit format 730. The native instructions availablein the 64-bit format 730 vary by embodiment. In some embodiments, theinstruction is compacted in part using a set of index values in an indexfield 713. The execution unit hardware references a set of compactiontables based on the index values and uses the compaction table outputsto reconstruct a native instruction in the 128-bit instruction format710. Other sizes and formats of instruction can be used.

For each format, instruction opcode 712 defines the operation that theexecution unit is to perform. The execution units execute eachinstruction in parallel across the multiple data elements of eachoperand. For example, in response to an add instruction the executionunit performs a simultaneous add operation across each color channelrepresenting a texture element or picture element. By default, theexecution unit performs each instruction across all data channels of theoperands. In some embodiments, instruction control field 714 enablescontrol over certain execution options, such as channels selection(e.g., predication) and data channel order (e.g., swizzle). Forinstructions in the 128-bit instruction format 710 an exec-size field716 limits the number of data channels that will be executed inparallel. In some embodiments, exec-size field 716 is not available foruse in the 64-bit compact instruction format 730.

Some execution unit instructions have up to three operands including twosource operands, src0 720, src1 722, and one destination 718. In someembodiments, the execution units support dual destination instructions,where one of the destinations is implied. Data manipulation instructionscan have a third source operand (e.g., SRC2 724), where the instructionopcode 712 determines the number of source operands. An instruction'slast source operand can be an immediate (e.g., hard-coded) value passedwith the instruction.

In some embodiments, the 128-bit instruction format 710 includes anaccess/address mode field 726 specifying, for example, whether directregister addressing mode or indirect register addressing mode is used.When direct register addressing mode is used, the register address ofone or more operands is directly provided by bits in the instruction.

In some embodiments, the 128-bit instruction format 710 includes anaccess/address mode field 726, which specifies an address mode and/or anaccess mode for the instruction. In one embodiment the access mode isused to define a data access alignment for the instruction. Someembodiments support access modes including a 16-byte aligned access modeand a 1-byte aligned access mode, where the byte alignment of the accessmode determines the access alignment of the instruction operands. Forexample, when in a first mode, the instruction may use byte-alignedaddressing for source and destination operands and when in a secondmode, the instruction may use 16-byte-aligned addressing for all sourceand destination operands.

In one embodiment, the address mode portion of the access/address modefield 726 determines whether the instruction is to use direct orindirect addressing. When direct register addressing mode is used bitsin the instruction directly provide the register address of one or moreoperands. When indirect register addressing mode is used, the registeraddress of one or more operands may be computed based on an addressregister value and an address immediate field in the instruction.

In some embodiments instructions are grouped based on opcode 712bit-fields to simplify Opcode decode 740. For an 8-bit opcode, bits 4,5, and 6 allow the execution unit to determine the type of opcode. Theprecise opcode grouping shown is merely an example. In some embodiments,a move and logic opcode group 742 includes data movement and logicinstructions (e.g., move (mov), compare (cmp)). In some embodiments,move and logic group 742 shares the five most significant bits (MSB),where move (mov) instructions are in the form of 0000xxxxb and logicinstructions are in the form of 0001xxxxb. A flow control instructiongroup 744 (e.g., call, jump (jmp)) includes instructions in the form of0010xxxxb (e.g., 0x20). A miscellaneous instruction group 746 includes amix of instructions, including synchronization instructions (e.g., wait,send) in the form of 0011xxxxb (e.g., 0x30). A parallel math instructiongroup 748 includes component-wise arithmetic instructions (e.g., add,multiply (mul)) in the form of 0100xxxxb (e.g., 0x40). The parallel mathgroup 748 performs the arithmetic operations in parallel across datachannels. The vector math group 750 includes arithmetic instructions(e.g., dp4) in the form of 0101xxxxb (e.g., 0x50). The vector math groupperforms arithmetic such as dot product calculations on vector operands.The illustrated opcode decode 740, in one embodiment, can be used todetermine which portion of an execution unit will be used to execute adecoded instruction. For example, some instructions may be designated assystolic instructions that will be performed by a systolic array. Otherinstructions, such as ray-tracing instructions (not shown) can be routedto a ray-tracing core or ray-tracing logic within a slice or partitionof execution logic.

Graphics Pipeline

FIG. 8 is a block diagram of another embodiment of a graphics processor800. Elements of FIG. 8 having the same reference numbers (or names) asthe elements of any other figure herein can operate or function in anymanner similar to that described elsewhere herein, but are not limitedto such.

In some embodiments, graphics processor 800 includes a geometry pipeline820, a media pipeline 830, a display engine 840, thread execution logic850, and a render output pipeline 870. In some embodiments, graphicsprocessor 800 is a graphics processor within a multi-core processingsystem that includes one or more general-purpose processing cores. Thegraphics processor is controlled by register writes to one or morecontrol registers (not shown) or via commands issued to graphicsprocessor 800 via a ring interconnect 802. In some embodiments, ringinterconnect 802 couples graphics processor 800 to other processingcomponents, such as other graphics processors or general-purposeprocessors. Commands from ring interconnect 802 are interpreted by acommand streamer 803, which supplies instructions to individualcomponents of the geometry pipeline 820 or the media pipeline 830.

In some embodiments, command streamer 803 directs the operation of avertex fetcher 805 that reads vertex data from memory and executesvertex-processing commands provided by command streamer 803. In someembodiments, vertex fetcher 805 provides vertex data to a vertex shader807, which performs coordinate space transformation and lightingoperations to each vertex. In some embodiments, vertex fetcher 805 andvertex shader 807 execute vertex-processing instructions by dispatchingexecution threads to execution units 852A-852B via a thread dispatcher831.

In some embodiments, execution units 852A-852B are an array of vectorprocessors having an instruction set for performing graphics and mediaoperations. In some embodiments, execution units 852A-852B have anattached L1 cache 851 that is specific for each array or shared betweenthe arrays. The cache can be configured as a data cache, an instructioncache, or a single cache that is partitioned to contain data andinstructions in different partitions.

In some embodiments, geometry pipeline 820 includes tessellationcomponents to perform hardware-accelerated tessellation of 3D objects.In some embodiments, a programmable hull shader 811 configures thetessellation operations. A programmable domain shader 817 providesback-end evaluation of tessellation output. A tessellator 813 operatesat the direction of hull shader 811 and contains special purpose logicto generate a set of detailed geometric objects based on a coarsegeometric model that is provided as input to geometry pipeline 820. Insome embodiments, if tessellation is not used, tessellation components(e.g., hull shader 811, tessellator 813, and domain shader 817) can bebypassed.

In some embodiments, complete geometric objects can be processed by ageometry shader 819 via one or more threads dispatched to executionunits 852A-852B, or can proceed directly to the clipper 829. In someembodiments, the geometry shader operates on entire geometric objects,rather than vertices or patches of vertices as in previous stages of thegraphics pipeline. If the tessellation is disabled the geometry shader819 receives input from the vertex shader 807. In some embodiments,geometry shader 819 is programmable by a geometry shader program toperform geometry tessellation if the tessellation units are disabled.

Before rasterization, a clipper 829 processes vertex data. The clipper829 may be a fixed function clipper or a programmable clipper havingclipping and geometry shader functions. In some embodiments, arasterizer and depth test component 873 in the render output pipeline870 dispatches pixel shaders to convert the geometric objects into perpixel representations. In some embodiments, pixel shader logic isincluded in thread execution logic 850. In some embodiments, anapplication can bypass the rasterizer and depth test component 873 andaccess un-rasterized vertex data via a stream out unit 823.

The graphics processor 800 has an interconnect bus, interconnect fabric,or some other interconnect mechanism that allows data and messagepassing amongst the major components of the processor. In someembodiments, execution units 852A-852B and associated logic units (e.g.,L1 cache 851, sampler 854, texture cache 858, etc.) interconnect via adata port 856 to perform memory access and communicate with renderoutput pipeline components of the processor. In some embodiments,sampler 854, caches 851, 858 and execution units 852A-852B each haveseparate memory access paths. In one embodiment the texture cache 858can also be configured as a sampler cache.

In some embodiments, render output pipeline 870 contains a rasterizerand depth test component 873 that converts vertex-based objects into anassociated pixel-based representation. In some embodiments, therasterizer logic includes a windower/masker unit to perform fixedfunction triangle and line rasterization. An associated render cache 878and depth cache 879 are also available in some embodiments. A pixeloperations component 877 performs pixel-based operations on the data,though in some instances, pixel operations associated with 2D operations(e.g. bit block image transfers with blending) are performed by the 2Dengine 841, or substituted at display time by the display controller 843using overlay display planes. In some embodiments, a shared L3 cache 875is available to all graphics components, allowing the sharing of datawithout the use of main system memory.

In some embodiments, graphics processor media pipeline 830 includes amedia engine 837 and a video front-end 834. In some embodiments, videofront-end 834 receives pipeline commands from the command streamer 803.In some embodiments, media pipeline 830 includes a separate commandstreamer. In some embodiments, video front-end 834 processes mediacommands before sending the command to the media engine 837. In someembodiments, media engine 837 includes thread spawning functionality tospawn threads for dispatch to thread execution logic 850 via threaddispatcher 831.

In some embodiments, graphics processor 800 includes a display engine840. In some embodiments, display engine 840 is external to processor800 and couples with the graphics processor via the ring interconnect802, or some other interconnect bus or fabric. In some embodiments,display engine 840 includes a 2D engine 841 and a display controller843. In some embodiments, display engine 840 contains special purposelogic capable of operating independently of the 3D pipeline. In someembodiments, display controller 843 couples with a display device (notshown), which may be a system integrated display device, as in a laptopcomputer, or an external display device attached via a display deviceconnector.

In some embodiments, the geometry pipeline 820 and media pipeline 830are configurable to perform operations based on multiple graphics andmedia programming interfaces and are not specific to any one applicationprogramming interface (API). In some embodiments, driver software forthe graphics processor translates API calls that are specific to aparticular graphics or media library into commands that can be processedby the graphics processor. In some embodiments, support is provided forthe Open Graphics Library (OpenGL), Open Computing Language (OpenCL),and/or Vulkan graphics and compute API, all from the Khronos Group. Insome embodiments, support may also be provided for the Direct3D libraryfrom the Microsoft Corporation. In some embodiments, a combination ofthese libraries may be supported. Support may also be provided for theOpen Source Computer Vision Library (OpenCV). A future API with acompatible 3D pipeline would also be supported if a mapping can be madefrom the pipeline of the future API to the pipeline of the graphicsprocessor.

Graphics Pipeline Programming

FIG. 9A is a block diagram illustrating a graphics processor commandformat 900 according to some embodiments. FIG. 9B is a block diagramillustrating a graphics processor command sequence 910 according to anembodiment. The solid lined boxes in FIG. 9A illustrate the componentsthat are generally included in a graphics command while the dashed linesinclude components that are optional or that are only included in asub-set of the graphics commands. The exemplary graphics processorcommand format 900 of FIG. 9A includes data fields to identify a client902, a command operation code (opcode) 904, and data 906 for thecommand. A sub-opcode 905 and a command size 908 are also included insome commands.

In some embodiments, client 902 specifies the client unit of thegraphics device that processes the command data. In some embodiments, agraphics processor command parser examines the client field of eachcommand to condition the further processing of the command and route thecommand data to the appropriate client unit. In some embodiments, thegraphics processor client units include a memory interface unit, arender unit, a 2D unit, a 3D unit, and a media unit. Each client unithas a corresponding processing pipeline that processes the commands.Once the command is received by the client unit, the client unit readsthe opcode 904 and, if present, sub-opcode 905 to determine theoperation to perform. The client unit performs the command usinginformation in data field 906. For some commands an explicit commandsize 908 is expected to specify the size of the command. In someembodiments, the command parser automatically determines the size of atleast some of the commands based on the command opcode. In someembodiments commands are aligned via multiples of a double word. Othercommand formats can be used.

The flow diagram in FIG. 9B illustrates an exemplary graphics processorcommand sequence 910. In some embodiments, software or firmware of adata processing system that features an embodiment of a graphicsprocessor uses a version of the command sequence shown to set up,execute, and terminate a set of graphics operations. A sample commandsequence is shown and described for purposes of example only asembodiments are not limited to these specific commands or to thiscommand sequence. Moreover, the commands may be issued as batch ofcommands in a command sequence, such that the graphics processor willprocess the sequence of commands in at least partially concurrence.

In some embodiments, the graphics processor command sequence 910 maybegin with a pipeline flush command 912 to cause any active graphicspipeline to complete the currently pending commands for the pipeline. Insome embodiments, the 3D pipeline 922 and the media pipeline 924 do notoperate concurrently. The pipeline flush is performed to cause theactive graphics pipeline to complete any pending commands. In responseto a pipeline flush, the command parser for the graphics processor willpause command processing until the active drawing engines completepending operations and the relevant read caches are invalidated.Optionally, any data in the render cache that is marked ‘dirty’ can beflushed to memory. In some embodiments, pipeline flush command 912 canbe used for pipeline synchronization or before placing the graphicsprocessor into a low power state.

In some embodiments, a pipeline select command 913 is used when acommand sequence requires the graphics processor to explicitly switchbetween pipelines. In some embodiments, a pipeline select command 913 isrequired only once within an execution context before issuing pipelinecommands unless the context is to issue commands for both pipelines. Insome embodiments, a pipeline flush command 912 is required immediatelybefore a pipeline switch via the pipeline select command 913.

In some embodiments, a pipeline control command 914 configures agraphics pipeline for operation and is used to program the 3D pipeline922 and the media pipeline 924. In some embodiments, pipeline controlcommand 914 configures the pipeline state for the active pipeline. Inone embodiment, the pipeline control command 914 is used for pipelinesynchronization and to clear data from one or more cache memories withinthe active pipeline before processing a batch of commands.

In some embodiments, return buffer state commands 916 are used toconfigure a set of return buffers for the respective pipelines to writedata. Some pipeline operations require the allocation, selection, orconfiguration of one or more return buffers into which the operationswrite intermediate data during processing. In some embodiments, thegraphics processor also uses one or more return buffers to store outputdata and to perform cross thread communication. In some embodiments, thereturn buffer state 916 includes selecting the size and number of returnbuffers to use for a set of pipeline operations.

The remaining commands in the command sequence differ based on theactive pipeline for operations. Based on a pipeline determination 920,the command sequence is tailored to the 3D pipeline 922 beginning withthe 3D pipeline state 930 or the media pipeline 924 beginning at themedia pipeline state 940.

The commands to configure the 3D pipeline state 930 include 3D statesetting commands for vertex buffer state, vertex element state, constantcolor state, depth buffer state, and other state variables that are tobe configured before 3D primitive commands are processed. The values ofthese commands are determined at least in part based on the particular3D API in use. In some embodiments, 3D pipeline state 930 commands arealso able to selectively disable or bypass certain pipeline elements ifthose elements will not be used.

In some embodiments, 3D primitive 932 command is used to submit 3Dprimitives to be processed by the 3D pipeline. Commands and associatedparameters that are passed to the graphics processor via the 3Dprimitive 932 command are forwarded to the vertex fetch function in thegraphics pipeline. The vertex fetch function uses the 3D primitive 932command data to generate vertex data structures. The vertex datastructures are stored in one or more return buffers. In someembodiments, 3D primitive 932 command is used to perform vertexoperations on 3D primitives via vertex shaders. To process vertexshaders, 3D pipeline 922 dispatches shader execution threads to graphicsprocessor execution units.

In some embodiments, 3D pipeline 922 is triggered via an execute 934command or event. In some embodiments, a register write triggers commandexecution. In some embodiments execution is triggered via a ‘go’ or‘kick’ command in the command sequence. In one embodiment, commandexecution is triggered using a pipeline synchronization command to flushthe command sequence through the graphics pipeline. The 3D pipeline willperform geometry processing for the 3D primitives. Once operations arecomplete, the resulting geometric objects are rasterized and the pixelengine colors the resulting pixels. Additional commands to control pixelshading and pixel back end operations may also be included for thoseoperations.

In some embodiments, the graphics processor command sequence 910 followsthe media pipeline 924 path when performing media operations. Ingeneral, the specific use and manner of programming for the mediapipeline 924 depends on the media or compute operations to be performed.Specific media decode operations may be offloaded to the media pipelineduring media decode. In some embodiments, the media pipeline can also bebypassed and media decode can be performed in whole or in part usingresources provided by one or more general-purpose processing cores. Inone embodiment, the media pipeline also includes elements forgeneral-purpose graphics processor unit (GPGPU) operations, where thegraphics processor is used to perform SIMD vector operations usingcomputational shader programs that are not explicitly related to therendering of graphics primitives.

In some embodiments, media pipeline 924 is configured in a similarmanner as the 3D pipeline 922. A set of commands to configure the mediapipeline state 940 are dispatched or placed into a command queue beforethe media object commands 942. In some embodiments, commands for themedia pipeline state 940 include data to configure the media pipelineelements that will be used to process the media objects. This includesdata to configure the video decode and video encode logic within themedia pipeline, such as encode or decode format. In some embodiments,commands for the media pipeline state 940 also support the use of one ormore pointers to “indirect” state elements that contain a batch of statesettings.

In some embodiments, media object commands 942 supply pointers to mediaobjects for processing by the media pipeline. The media objects includememory buffers containing video data to be processed. In someembodiments, all media pipeline states must be valid before issuing amedia object command 942. Once the pipeline state is configured andmedia object commands 942 are queued, the media pipeline 924 istriggered via an execute command 944 or an equivalent execute event(e.g., register write). Output from media pipeline 924 may then be postprocessed by operations provided by the 3D pipeline 922 or the mediapipeline 924. In some embodiments, GPGPU operations are configured andexecuted in a similar manner as media operations.

Graphics Software Architecture

FIG. 10 illustrates an exemplary graphics software architecture for adata processing system 1000 according to some embodiments. In someembodiments, software architecture includes a 3D graphics application1010, an operating system 1020, and at least one processor 1030. In someembodiments, processor 1030 includes a graphics processor 1032 and oneor more general-purpose processor core(s) 1034. The graphics application1010 and operating system 1020 each execute in the system memory 1050 ofthe data processing system.

In some embodiments, 3D graphics application 1010 contains one or moreshader programs including shader instructions 1012. The shader languageinstructions may be in a high-level shader language, such as theHigh-Level Shader Language (HLSL) of Direct3D, the OpenGL ShaderLanguage (GLSL), and so forth. The application also includes executableinstructions 1014 in a machine language suitable for execution by thegeneral-purpose processor core 1034. The application also includesgraphics objects 1016 defined by vertex data.

In some embodiments, operating system 1020 is a Microsoft® Windows®operating system from the Microsoft Corporation, a proprietary UNIX-likeoperating system, or an open source UNIX-like operating system using avariant of the Linux kernel. The operating system 1020 can support agraphics API 1022 such as the Direct3D API, the OpenGL API, or theVulkan API. When the Direct3D API is in use, the operating system 1020uses a front-end shader compiler 1024 to compile any shader instructions1012 in HLSL into a lower-level shader language. The compilation may bea just-in-time (JIT) compilation or the application can perform shaderpre-compilation. In some embodiments, high-level shaders are compiledinto low-level shaders during the compilation of the 3D graphicsapplication 1010. In some embodiments, the shader instructions 1012 areprovided in an intermediate form, such as a version of the StandardPortable Intermediate Representation (SPIR) used by the Vulkan API.

In some embodiments, user mode graphics driver 1026 contains a back-endshader compiler 1027 to convert the shader instructions 1012 into ahardware specific representation. When the OpenGL API is in use, shaderinstructions 1012 in the GLSL high-level language are passed to a usermode graphics driver 1026 for compilation. In some embodiments, usermode graphics driver 1026 uses operating system kernel mode functions1028 to communicate with a kernel mode graphics driver 1029. In someembodiments, kernel mode graphics driver 1029 communicates with graphicsprocessor 1032 to dispatch commands and instructions.

IP Core Implementations

One or more aspects of at least one embodiment may be implemented byrepresentative code stored on a machine-readable medium which representsand/or defines logic within an integrated circuit such as a processor.For example, the machine-readable medium may include instructions whichrepresent various logic within the processor. When read by a machine,the instructions may cause the machine to fabricate the logic to performthe techniques described herein. Such representations, known as “IPcores,” are reusable units of logic for an integrated circuit that maybe stored on a tangible, machine-readable medium as a hardware modelthat describes the structure of the integrated circuit. The hardwaremodel may be supplied to various customers or manufacturing facilities,which load the hardware model on fabrication machines that manufacturethe integrated circuit. The integrated circuit may be fabricated suchthat the circuit performs operations described in association with anyof the embodiments described herein.

FIG. 11A is a block diagram illustrating an IP core development system1100 that may be used to manufacture an integrated circuit to performoperations according to an embodiment. The IP core development system1100 may be used to generate modular, re-usable designs that can beincorporated into a larger design or used to construct an entireintegrated circuit (e.g., an SOC integrated circuit). A design facility1130 can generate a software simulation 1110 of an IP core design in ahigh-level programming language (e.g., C/C++). The software simulation1110 can be used to design, test, and verify the behavior of the IP coreusing a simulation model 1112. The simulation model 1112 may includefunctional, behavioral, and/or timing simulations. A register transferlevel (RTL) design 1115 can then be created or synthesized from thesimulation model 1112. The RTL design 1115 is an abstraction of thebehavior of the integrated circuit that models the flow of digitalsignals between hardware registers, including the associated logicperformed using the modeled digital signals. In addition to an RTLdesign 1115, lower-level designs at the logic level or transistor levelmay also be created, designed, or synthesized. Thus, the particulardetails of the initial design and simulation may vary.

The RTL design 1115 or equivalent may be further synthesized by thedesign facility into a hardware model 1120, which may be in a hardwaredescription language (HDL), or some other representation of physicaldesign data. The HDL may be further simulated or tested to verify the IPcore design. The IP core design can be stored for delivery to a 3rdparty fabrication facility 1165 using non-volatile memory 1140 (e.g.,hard disk, flash memory, or any non-volatile storage medium).Alternatively, the IP core design may be transmitted (e.g., via theInternet) over a wired connection 1150 or wireless connection 1160. Thefabrication facility 1165 may then fabricate an integrated circuit thatis based at least in part on the IP core design. The fabricatedintegrated circuit can be configured to perform operations in accordancewith at least one embodiment described herein.

FIG. 11B illustrates a cross-section side view of an integrated circuitpackage assembly 1170, according to some embodiments described herein.The integrated circuit package assembly 1170 illustrates animplementation of one or more processor or accelerator devices asdescribed herein. The package assembly 1170 includes multiple units ofhardware logic 1172, 1174 connected to a substrate 1180. The logic 1172,1174 may be implemented at least partly in configurable logic orfixed-functionality logic hardware, and can include one or more portionsof any of the processor core(s), graphics processor(s), or otheraccelerator devices described herein. Each unit of logic 1172, 1174 canbe implemented within a semiconductor die and coupled with the substrate1180 via an interconnect structure 1173. The interconnect structure 1173may be configured to route electrical signals between the logic 1172,1174 and the substrate 1180, and can include interconnects such as, butnot limited to bumps or pillars. In some embodiments, the interconnectstructure 1173 may be configured to route electrical signals such as,for example, input/output (I/O) signals and/or power or ground signalsassociated with the operation of the logic 1172, 1174. In someembodiments, the substrate 1180 is an epoxy-based laminate substrate.The substrate 1180 may include other suitable types of substrates inother embodiments. The package assembly 1170 can be connected to otherelectrical devices via a package interconnect 1183. The packageinterconnect 1183 may be coupled to a surface of the substrate 1180 toroute electrical signals to other electrical devices, such as amotherboard, other chipset, or multi-chip module.

In some embodiments, the units of logic 1172, 1174 are electricallycoupled with a bridge 1182 that is configured to route electricalsignals between the logic 1172, 1174. The bridge 1182 may be a denseinterconnect stricture that provides a route for electrical signals. Thebridge 1182 may include a bridge substrate composed of glass or asuitable semiconductor material. Electrical routing features can beformed on the bridge substrate to provide a chip-to-chip connectionbetween the logic 1172, 1174.

Although two units of logic 1172, 1174 and a bridge 1182 areillustrated, embodiments described herein may include more or fewerlogic units on one or more dies. The one or more dies may be connectedby zero or more bridges, as the bridge 1182 may be excluded when thelogic is included on a single die. Alternatively, multiple dies or unitsof logic can be connected by one or more bridges. Additionally, multiplelogic units, dies, and bridges can be connected together in otherpossible configurations, including three-dimensional configurations.

FIG. 11C illustrates a package assembly 1190 that includes multipleunits of hardware logic chiplets connected to a substrate 1180 (e.g.,base die). A graphics processing unit, parallel processor, and/orcompute accelerator as described herein can be composed from diversesilicon chiplets that are separately manufactured. In this context, achiplet is an at least partially packaged integrated circuit thatincludes distinct units of logic that can be assembled with otherchiplets into a larger package. A diverse set of chiplets with differentIP core logic can be assembled into a single device. Additionally, thechiplets can be integrated into a base die or base chiplet using activeinterposer technology. The concepts described herein enable theinterconnection and communication between the different forms of IPwithin the GPU. IP cores can be manufactured using different processtechnologies and composed during manufacturing, which avoids thecomplexity of converging multiple IPs, especially on a large SoC withseveral flavors IPs, to the same manufacturing process. Enabling the useof multiple process technologies improves the time to market andprovides a cost-effective way to create multiple product SKUs.Additionally, the disaggregated IPs are more amenable to being powergated independently, components that are not in use on a given workloadcan be powered off, reducing overall power consumption.

The hardware logic chiplets can include special purpose hardware logicchiplets 1172, logic or I/O chiplets 1174, and/or memory chiplets 1175.The hardware logic chiplets 1172 and logic or I/O chiplets 1174 may beimplemented at least partly in configurable logic or fixed-functionalitylogic hardware and can include one or more portions of any of theprocessor core(s), graphics processor(s), parallel processors, or otheraccelerator devices described herein. The memory chiplets 1175 can beDRAM (e.g., GDDR, HBM) memory or cache (SRAM) memory.

Each chiplet can be fabricated as separate semiconductor die and coupledwith the substrate 1180 via an interconnect structure 1173. Theinterconnect structure 1173 may be configured to route electricalsignals between the various chiplets and logic within the substrate1180. The interconnect structure 1173 can include interconnects such as,but not limited to bumps or pillars. In some embodiments, theinterconnect structure 1173 may be configured to route electricalsignals such as, for example, input/output (I/O) signals and/or power orground signals associated with the operation of the logic, I/O, andmemory chiplets.

In some embodiments, the substrate 1180 is an epoxy-based laminatesubstrate. The substrate 1180 may include other suitable types ofsubstrates in other embodiments. The package assembly 1190 can beconnected to other electrical devices via a package interconnect 1183.The package interconnect 1183 may be coupled to a surface of thesubstrate 1180 to route electrical signals to other electrical devices,such as a motherboard, other chipset, or multi-chip module.

In some embodiments, a logic or I/O chiplet 1174 and a memory chiplet1175 can be electrically coupled via a bridge 1187 that is configured toroute electrical signals between the logic or I/O chiplet 1174 and amemory chiplet 1175. The bridge 1187 may be a dense interconnectstructure that provides a route for electrical signals. The bridge 1187may include a bridge substrate composed of glass or a suitablesemiconductor material. Electrical routing features can be formed on thebridge substrate to provide a chip-to-chip connection between the logicor I/O chiplet 1174 and a memory chiplet 1175. The bridge 1187 may alsobe referred to as a silicon bridge or an interconnect bridge. Forexample, the bridge 1187, in some embodiments, is an Embedded Multi-dieInterconnect Bridge (EMIB). In some embodiments, the bridge 1187 maysimply be a direct connection from one chiplet to another chiplet.

The substrate 1180 can include hardware components for I/O 1191, cachememory 1192, and other hardware logic 1193. A fabric 1185 can beembedded in the substrate 1180 to enable communication between thevarious logic chiplets and the logic 1191, 1193 within the substrate1180. In one embodiment, the I/O 1191, fabric 1185, cache, bridge, andother hardware logic 1193 can be integrated into a base die that islayered on top of the substrate 1180. The fabric 1185 may be a networkon a chip interconnect or another form of packet switched fabric thatswitches data packets between components of the package assembly.

In various embodiments a package assembly 1190 can include fewer orgreater number of components and chiplets that are interconnected by afabric 1185 or one or more bridges 1187. The chiplets within the packageassembly 1190 may be arranged in a 3D or 2.5D arrangement. In general,bridge structures 1187 may be used to facilitate a point to pointinterconnect between, for example, logic or I/O chiplets and memorychiplets. The fabric 1185 can be used to interconnect the various logicand/or I/O chiplets (e.g., chiplets 1172, 1174, 1191, 1193). with otherlogic and/or I/O chiplets. In one embodiment, the cache memory 1192within the substrate can act as a global cache for the package assembly1190, part of a distributed global cache, or as a dedicated cache forthe fabric 1185.

FIG. 11D illustrates a package assembly 1194 including interchangeablechiplets 1195, according to an embodiment. The interchangeable chiplets1195 can be assembled into standardized slots on one or more basechiplets 1196, 1198. The base chiplets 1196, 1198 can be coupled via abridge interconnect 1197, which can be similar to the other bridgeinterconnects described herein and may be, for example, an EMIB. Memorychiplets can also be connected to logic or I/O chiplets via a bridgeinterconnect. I/O and logic chiplets can communicate via an interconnectfabric. The base chiplets can each support one or more slots in astandardized format for one of logic or I/O or memory/cache.

In one embodiment, SRAM and power delivery circuits can be fabricatedinto one or more of the base chiplets 1196, 1198, which can befabricated using a different process technology relative to theinterchangeable chiplets 1195 that are stacked on top of the basechiplets. For example, the base chiplets 1196, 1198 can be fabricatedusing a larger process technology, while the interchangeable chipletscan be manufactured using a smaller process technology. One or more ofthe interchangeable chiplets 1195 may be memory (e.g., DRAM) chiplets.Different memory densities can be selected for the package assembly 1194based on the power, and/or performance targeted for the product thatuses the package assembly 1194. Additionally, logic chiplets with adifferent number of type of functional units can be selected at time ofassembly based on the power, and/or performance targeted for theproduct. Additionally, chiplets containing IP logic cores of differingtypes can be inserted into the interchangeable chiplet slots, enablinghybrid processor designs that can mix and match different technology IPblocks.

Exemplary System on a Chip Integrated Circuit

FIG. 12-13B illustrate exemplary integrated circuits and associatedgraphics processors that may be fabricated using one or more IP cores,according to various embodiments described herein. In addition to whatis illustrated, other logic and circuits may be included, includingadditional graphics processors/cores, peripheral interface controllers,or general-purpose processor cores.

FIG. 12 is a block diagram illustrating an exemplary system on a chipintegrated circuit 1200 that may be fabricated using one or more IPcores, according to an embodiment. Exemplary integrated circuit 1200includes one or more application processor(s) 1205 (e.g., CPUs), atleast one graphics processor 1210, and may additionally include an imageprocessor 1215 and/or a video processor 1220, any of which may be amodular IP core from the same or multiple different design facilities.Integrated circuit 1200 includes peripheral or bus logic including a USBcontroller 1225, UART controller 1230, an SPI/SDIO controller 1235, andan I²S/I²C controller 1240. Additionally, the integrated circuit caninclude a display device 1245 coupled to one or more of ahigh-definition multimedia interface (HDMI) controller 1250 and a mobileindustry processor interface (MIPI) display interface 1255. Storage maybe provided by a flash memory subsystem 1260 including flash memory anda flash memory controller. Memory interface may be provided via a memorycontroller 1265 for access to SDRAM or SRAM memory devices. Someintegrated circuits additionally include an embedded security engine1270.

FIG. 13A-13B are block diagrams illustrating exemplary graphicsprocessors for use within an SoC, according to embodiments describedherein. FIG. 13A illustrates an exemplary graphics processor 1310 of asystem on a chip integrated circuit that may be fabricated using one ormore IP cores, according to an embodiment. FIG. 13B illustrates anadditional exemplary graphics processor 1340 of a system on a chipintegrated circuit that may be fabricated using one or more IP cores,according to an embodiment. Graphics processor 1310 of FIG. 13A is anexample of a low power graphics processor core. Graphics processor 1340of FIG. 13B is an example of a higher performance graphics processorcore. Each of the graphics processors 1310, 1340 can be variants of thegraphics processor 1210 of FIG. 12 .

As shown in FIG. 13A, graphics processor 1310 includes a vertexprocessor 1305 and one or more fragment processor(s) 1315A-1315N (e.g.,1315A, 1315B, 1315C, 1315D, through 1315N-1, and 1315N). Graphicsprocessor 1310 can execute different shader programs via separate logic,such that the vertex processor 1305 is optimized to execute operationsfor vertex shader programs, while the one or more fragment processor(s)1315A-1315N execute fragment (e.g., pixel) shading operations forfragment or pixel shader programs. The vertex processor 1305 performsthe vertex processing stage of the 3D graphics pipeline and generatesprimitives and vertex data. The fragment processor(s) 1315A-1315N usethe primitive and vertex data generated by the vertex processor 1305 toproduce a framebuffer that is displayed on a display device. In oneembodiment, the fragment processor(s) 1315A-1315N are optimized toexecute fragment shader programs as provided for in the OpenGL API,which may be used to perform similar operations as a pixel shaderprogram as provided for in the Direct 3D API.

Graphics processor 1310 additionally includes one or more memorymanagement units (MMUs) 1320A-1320B, cache(s) 1325A-1325B, and circuitinterconnect(s) 1330A-1330B. The one or more MMU(s) 1320A-1320B providefor virtual to physical address mapping for the graphics processor 1310,including for the vertex processor 1305 and/or fragment processor(s)1315A-1315N, which may reference vertex or image/texture data stored inmemory, in addition to vertex or image/texture data stored in the one ormore cache(s) 1325A-1325B. In one embodiment the one or more MMU(s)1320A-1320B may be synchronized with other MMUs within the system,including one or more MMUs associated with the one or more applicationprocessor(s) 1205, image processor 1215, and/or video processor 1220 ofFIG. 12 , such that each processor 1205-1220 can participate in a sharedor unified virtual memory system. The one or more circuitinterconnect(s) 1330A-1330B enable graphics processor 1310 to interfacewith other IP cores within the SoC, either via an internal bus of theSoC or via a direct connection, according to embodiments.

As shown FIG. 13B, graphics processor 1340 includes the one or moreMMU(s) 1320A-1320B, cache(s) 1325A-1325B, and circuit interconnect(s)1330A-1330B of the graphics processor 1310 of FIG. 13A. Graphicsprocessor 1340 includes one or more shader core(s) 1355A-1355N (e.g.,1355A, 1355B, 1355C, 1355D, 1355E, 1355F, through 1355N-1, and 1355N),which provides for a unified shader core architecture in which a singlecore or type or core can execute all types of programmable shader code,including shader program code to implement vertex shaders, fragmentshaders, and/or compute shaders. The exact number of shader corespresent can vary among embodiments and implementations. Additionally,graphics processor 1340 includes an inter-core task manager 1345, whichacts as a thread dispatcher to dispatch execution threads to one or moreshader cores 1355A-1355N and a tiling unit 1358 to accelerate tilingoperations for tile-based rendering, in which rendering operations for ascene are subdivided in image space, for example to exploit localspatial coherence within a scene or to optimize use of internal caches.

Tensor Acceleration Logic for Machine Learning Workloads

FIG. 14 is a block diagram of a data processing system 1400, accordingto an embodiment. The data processing system 1400 is a heterogeneousprocessing system having a processor 1402, unified memory 1410, and aGPGPU 1420 including machine learning acceleration logic. The processor1402 and the GPGPU 1420 can be any of the processors and GPGPU/parallelprocessors as described herein. The processor 1402 can executeinstructions for a compiler 1415 stored in system memory 1412. Thecompiler 1415 executes on the processor 1402 to compile source code1414A into compiled code 1414B. The compiled code 1414B can includeinstructions that may be executed by the processor 1402 and/orinstructions that may be executed by the GPGPU 1420. During compilation,the compiler 1415 can perform operations to insert metadata, includinghints as to the level of data parallelism present in the compiled code1414B and/or hints regarding the data locality associated with threadsto be dispatched based on the compiled code 1414B. The compiler 1415 caninclude the information necessary to perform such operations or theoperations can be performed with the assistance of a runtime library1416. The runtime library 1416 can also assist the compiler 1415 in thecompilation of the source code 1414A and can also include instructionsthat are linked at runtime with the compiled code 1414B to facilitateexecution of the compiled instructions on the GPGPU 1420.

The unified memory 1410 represents a unified address space that may beaccessed by the processor 1402 and the GPGPU 1420. The unified memorycan include system memory 1412 as well as GPGPU memory 1418. The GPGPUmemory 1418 is memory within an address pace of the GPGPU 1420 and caninclude some or all of system memory 1412. In one embodiment the GPGPUmemory 1418 can also include at least a portion of any memory dedicatedfor use exclusively by the GPGPU 1420. In one embodiment, compiled code1414B stored in system memory 1412 can be mapped into GPGPU memory 1418for access by the GPGPU 1420.

The GPGPU 1420 includes multiple compute blocks 1424A-1424N, which caninclude one or more of a variety of processing resources describedherein. The processing resources can be or include a variety ofdifferent computational resources such as, for example, execution units,compute units, streaming multiprocessors, graphics multiprocessors, ormulti-core groups. In one embodiment the GPGPU 1420 additionallyincludes a tensor (e.g., matrix) accelerator 1423, which can include oneor more special function compute units that are designed to accelerate asubset of matrix operations (e.g., dot product, etc.). The tensoraccelerator 1423 may also be referred to as a tensor accelerator ortensor core. In one embodiment, logic components within the tensoraccelerator 1423 may be distributed across the processing resources ofthe multiple compute blocks 1424A-1424N.

The GPGPU 1420 can also include a set of resources that can be shared bythe compute blocks 1424A-1424N and the tensor accelerator 1423,including but not limited to a set of registers 1425, a power andperformance module 1426, and a cache 1427. In one embodiment theregisters 1425 include directly and indirectly accessible registers,where the indirectly accessible registers are optimized for use by thetensor accelerator 1423. The power and performance module 1426 can beconfigured to adjust power delivery and clock frequencies for thecompute blocks 1424A-1424N to power gate idle components within thecompute blocks 1424A-1424N. In various embodiments the cache 1427 caninclude an instruction cache and/or a lower level data cache.

The GPGPU 1420 can additionally include an L3 data cache 1430, which canbe used to cache data accessed from the unified memory 1410 by thetensor accelerator 1423 and/or the compute elements within the computeblocks 1424A-1424N. In one embodiment the L3 data cache 1430 includesshared local memory 1432 that can be shared by the compute elementswithin the compute blocks 1424A-1424N and the tensor accelerator 1423.

In one embodiment the GPGPU 1420 includes instruction handling logic,such as a fetch and decode unit 1421 and a scheduler controller 1422.The fetch and decode unit 1421 includes a fetch unit and decode unit tofetch and decode instructions for execution by one or more of thecompute blocks 1424A-1424N or the tensor accelerator 1423. Theinstructions can be scheduled to the appropriate functional unit withinthe compute block 1424A-1424N or the tensor accelerator via thescheduler controller 1422. In one embodiment the scheduler controller1422 is an ASIC configurable to perform advanced scheduling operations.In one embodiment the scheduler controller 1422 is a micro-controller ora low energy-per-instruction processing core capable of executingscheduler instructions loaded from a firmware module.

In one embodiment some functions to be performed by the compute blocks1424A-1424N can be directly scheduled to or offloaded to the tensoraccelerator 1423. In various embodiments the tensor accelerator 1423includes processing element logic configured to efficiently performmatrix compute operations, such as multiply and add operations and dotproduct operations used by 3D graphics or compute shader programs. Inone embodiment the tensor accelerator 1423 can be configured toaccelerate operations used by machine learning frameworks. In oneembodiment the tensor accelerator 1423 is an application specificintegrated circuit explicitly configured to perform a specific set ofparallel matrix multiplication and/or addition operations. In oneembodiment the tensor accelerator 1423 is a field programmable gatearray (FPGA) that provides fixed function logic that can updated betweenworkloads. The set of matrix operations that can be performed by thetensor accelerator 1423 may be limited relative to the operations thatcan be performed by the compute block 1424A-1424N. However, the tensoraccelerator 1423 can perform those the operations at a significantlyhigher throughput relative to the compute block 1424A-1424N.

FIG. 15 illustrates a matrix operation 1505 performed by an instructionpipeline 1500, according to an embodiment. The instruction pipeline 1500can be configured to perform a matrix operation 1505, such as, but notlimited to a dot product operation. The dot product of two vectors is ascalar value that is equal to sum of products of correspondingcomponents of the vectors. The dot product can be calculated as shown inequation (1) below.

$\begin{matrix}{{\overset{\rightarrow}{a} \cdot \overset{\rightarrow}{b}} = {{\sum\limits_{i = 1}^{n}{a_{i}b_{i}}} = {{a_{1}b_{1}} + \ldots + {a_{n}b_{n}}}}} & (1)\end{matrix}$

The dot product can be used in a convolution operation for aconvolutional neural network (CNN). FIG. 15 illustrates atwo-dimensional (2D) convolution using a matrix operation 1505 includinga dot product operation. While 2D convolution is illustrated,N-dimensional convolution can be performed on an N-dimensional volumeusing N-dimensional filters. A receptive field tile 1502 highlights aportion of an input volume in an input volume buffer 1504. The inputvolume buffer can be stored in memory 1530. A dot product matrixoperation 1505 can be performed between the data within the receptivefield tile 1502 and a convolutional filter to generate a data pointwithin output buffer 1506, which can also be stored in memory 1530. Thememory 1530 can be any of the memory described herein, including systemmemory 1412, GPGPU memory 1418, or one or more cache memories 1427, 1430as in FIG. 14 .

The combination of the data points within the output buffer 1506represents an activation map generated by the convolution operation.Each point within the activation map is generated by sliding thereceptive field tile across the input volume buffer 1504. The activationmap data can be input to an activation function to determine an outputactivation value. In one embodiment, convolution of the input volumebuffer 1504 can be defined within a framework as high-level matrixoperation 1505. The high-level matrix operations can be performed viaprimitive operations, such as a basic linear algebra subprogram (BLAS)operation. The primitive operations can be accelerated via hardwareinstructions executed by the instruction pipeline 1500.

The instruction pipeline 1500 used to accelerate hardware instructionscan include the instruction fetch and decode unit 1421, which can fetchand decode hardware instructions, and the scheduler controller 1422which can schedule decoded instructions to one or more processingresources within the compute blocks 1424A-1424N and/or the tensoraccelerator 1423. In one embodiment, a hardware instruction can bescheduled to the compute blocks 1424A-1424N and offloaded to the tensoraccelerator 1423. The one or more hardware instructions and associateddata to perform the matrix operation 1505 can be stored in the memory1530. Output of the hardware instruction can also be stored in thememory 1530.

In one embodiment, the tensor accelerator 1423 can execute one or morehardware instructions to perform the matrix operation 1505 using anintegrated systolic array 1508 (DP logic). The systolic array 1508 caninclude a combination of programmable and fixed function hardware thatis configurable to perform dot product operations. While functionalunits within the compute blocks 1424A-1424N can also be configured toperform dot product operations, the systolic array 1508 can beconfigured to perform a limited subset of dot product operations at asignificantly higher throughput relative to the compute block1424A-1424N.

Scalable Sparse Matrix Multiply Acceleration Using Systolic Arrays withFeedback Inputs

Described herein is an architecture to enable scalable sparse matrixmultiply acceleration using systolic arrays with feedback inputs. Thearchitecture accelerates systolic matrix multiplication in workloadswhose data exhibits a high number of zeroes. This architecture is easilyscalable, preserving the gains given by the optimizations introduced totake advantage of the sparsity found in the workload's data, andallowing incrementing the instructions throughput. Advantages includereduced area, reduced power consumption, and increased performancerelative to other systolic arrays. This architecture improvesperformance of systolic dot product accumulate operations by reducingthe number of computations in highly sparse data loads. The reduction ofcomputations results in a reduction of power consumption when comparedwith previous architectures. This architecture also scales better thanexisting systolic arrays by simplifying the design of the systolicarray. The simplified design enables the architecture to be widelyincorporated in accelerator designs to increase the matrix processingthroughput of those accelerators.

Data used in computations of machine learning algorithms exhibit a highnumber of zeros as input elements. In neural network applications, thisis naturally caused by the topology of the implemented network and thecharacteristics of the modeled neurons. As an example, in a fullyinterconnected neural network, the outputs of a column or layer ofneurons are connected to an input of each neuron in the next layer. Anetwork is composed of many layers, each one possibly featuring a largenumber of neurons. The last stage in the computation of the output of aneuron is executing the activation function. This function usuallyoutputs the evaluation of a positive function when the computations ofthe neuron's inputs is positive, and outputs zero when they arenegative. Due to that, a large number of the output results of a neuroncan be zeroes, and in a following step in the computation of the neuralnetwork, fed to the next network layer.

In the execution of a neural network featuring a large number of layersand neurons, each layer is represented by a matrix of the values of theinput's weights of the neurons and a matrix of the values of the inputsto the neurons. All the inputs to a neuron are multiplied by its weightand added to the result of the other inputs to the neuron. After that,the activation function is applied to obtain the output of the neuronwhich feds the next network layer. To fast compute the multiplicationand addition of the inputs and weight of the neurons, several techniqueshave been used in hardware. The one that pertains to this invention isthe use of systolic arrays for multiply and accumulate operations.

FIG. 16 illustrates a systolic array 1600 including multiplier and addercircuits organized in a pipelined fashion. Inputs 1612A-1612H for thefirst input matrix are represented by the data elements contained in theinputs labeled Src1 and Src1+1 through Src1+7. Inputs 1610A-1610Bcorrespond to the second input matrix and are labeled as Src2. Input1602, which may include initial accumulator values, can be provided asSrc0. Processing elements 1611A-1611H of the systolic array 1600 operateas a pipelined structure and each stage is executed in a clock cycle. Onevery cycle, every stage can receive a new src2 input which can becomputed with a new Src1 input or an older one. A Src2 input operateswith eight Scr1 inputs (e.g., one Scr1 input per stage). The dataelements of a channel of the Src2 input are broadcast across allchannels of processing elements 1611A-1611H. The processing elementsthen operate the Src2 channel with all channels of a Src1 input. In afirst clock cycle, a Src1 input is operated with data elements of thefirst channel of Src2. In the next cycle, a second Src1 (labeled asSrc1+1) operates with the data elements of the second channel of Src2.This sequence repeats on the 8 stages of the pipeline. Each stage addsits operation to the output of the previous stage. Across the pipelinestages, multiple Src2 inputs are operated in a pipelined fashion. Assuccessive channels of a first Src2 input are pushed through thepipeline stages, a new Src2 input can be provided at the first stage.

Output 1622 from the final stage is labeled as Dst. Where d=the systolicdepth and e=the number of data elements per channel, the output of achannel is described by equation (2) below:

$\begin{matrix}{{Dst}_{i} = {{{Src}0_{i}} + {\sum\limits_{j = 0}^{d}{\sum\limits_{k = 0}^{e}{\left( {{{Src}1} + j} \right)_{{element}k{of}{channel}i}*{Src}2_{{element}k{of}{channel}j}}}}}} & (2)\end{matrix}$

As shown in equation (2), each channel can include multiple dataelements on which operations are performed in parallel. In oneembodiment, each channel represents a four element data vector, althougha different number of elements can be configured for each channel. Inone embodiment, the number of data elements within a channel can varybased on the size of each data element. Dot products can be performedusing, for example, four element vectors with 8-bit data types perelement, two element vectors with 16-bit data types, eight elementvectors with 4-bit data types (e.g., INT4), or 16 element vectors with2-bit data types (e.g., INT2). The number of channels can beautomatically adjusted depending on the datatype of Src1 and Src2. Aninstruction can also specify a required systolic depth to be used forthe instruction.

In one embodiment the processing elements 1611A-1611H may read inputs1610A-1610H, 1612A-1612H directly from the general-purpose registerfile. In one embodiment systolic array 1600 includes logic to readinputs 1610A-1610H, 1612A-1612H from the general purpose register fileand store input data in registers, buffers, or memory that is internalto the systolic array. Internal logic can then feed the input dataelements to the processing elements 1611A-1611H for processing. Output1622 can be written to internal registers or memory of the systolicarray 1600 and/or written directly to the general-purpose register file.

In one embodiment, when the elements that input to a multiplier/adder ina stage are determined to be zero, the multiplication/addition can bebypassed and only the previous input is propagated. When an input matrixis sparse (e.g., contains a high number of zeroes), the number ofoperations to be performed is reduced. Some implementations may bypassthe multiply/accumulate stages to avoiding spending power doing themultiply/add operation. However, simply bypassing an operation resultsin idle stages in the systolic chain. For example, if an element of aSrc2 input are all zeroes, bypassing that stage associated with thatelement will save power. However, no operations will be done in thatcycle. Thus, the throughput of the operations will remain unimproved.Other implementations may rearrange the inputs in such way that entiresections of the array can be bypassed. Rearranging the input increasesthe scale-up cost due to the addition of extra hardware to rearrange theinputs. The architecture has to consider cases of inputs with nosparsity, which will require using the full depth of the pipeline. Thus,the architecture should be designed with all the stages alwaysavailable.

Described herein, in various embodiments, are architectures withoptimizations to handle sparse inputs in a manner while avoiding theabove issues. Embodiments provide for a modular systolic array that canbe easily scalable to fulfill the needs of different products and allowthe computation of only non-zero elements without additional hardware oridle clock cycles. These concepts are incrementally described in thenext sections of this specification.

A Matrix Multiply Accelerator with Feedback Inputs

Systolic array 1600 is an eight deep multiply/add array withaccumulations and may be referred to as a DPAS (Dot Product AccumulateSystolic) array. The depth of such architecture is beneficial to someproducts, projects, and/or use cases. Other products, projects, and/oruse cases might not have the need for an array of that depth and wouldbenefit from having an array with lower throughput, but smaller areaand/or lower power consumption. Alternatively, other products, projects,and/or use cases might benefit from a higher DPAS throughput achievableby using a higher pipeline depth. To reduce the amount of hardware usedin a systolic array while conserving the same programming model that isused for deeper arrays, feedback inputs are added to a reduced depthversion of the systolic arrays shown in FIG. 16 .

FIG. 17A-17B illustrates the use of a four-deep systolic array 1700 tocompute an equivalent array of eight systolic stages. FIG. 17A shows thearray receiving Src0 inputs from an external source and processing thefirst four stages with Scr1 and Src2 inputs. The output of this array isfed back into the second step shown in FIG. 17B. FIG. 17B shows that thenext four stages are calculated using the feedback data that includesthe already processed values and the Scr1 and Src2 inputs.

As shown in FIG. 17A, systolic array 1700 can accept input 1602, as Src0input, which is read (1702) via data selector 1704. Data selector 1704selects between the input 1602 and feedback input 1706. Processingelements 1611A-1611D can process inputs 1610A-1610D and 1612A-1612D in asimilar manner as systolic array 1600. If four stages are sufficient tocomplete an operation, processing element 1611D can write (1722) output1622 to a specified Dst register or memory via data selector 1724. Wherefurther stages are required, data selector 1724 can write feedbackoutput 1726, which is provided as feedback input 1706 to processingelement 1611A.

As shown in FIG. 17B, in one embodiment feedback input 1706 can befurther processed by processing elements 1611A-1611D. Feedback input1706 includes the already processed values. In one embodiment, feedbackinput 1706 can also include input 1610E-1610H, input 1612E-1612H, whichcan be pre-fetched while processing the first four stages. Data selector1704 select feedback input 1706 for input by processing element 1611A.Processing elements 1611A-1611D can then process inputs 1610E-1610H and1612E-1612H. Data selector 1724 can then write (1722) the eighth stageresult as output 1622 to the specified Dst register.

Time diagrams of the arrays of FIG. 16 and FIG. 17A-17B are shown inFIG. 18A-18B.

FIG. 18A-18B show two timing diagrams 1800, 1850. FIG. 18A shows atiming diagram 1800 that corresponds to the 8-deep systolic array 1600depicted in FIG. 16 . FIG. 18B shows a time diagram 1850 thatcorresponds to the systolic array with feedback inputs depicted in FIG.17A-17B. Multiple clock cycles are shown.

As shown in FIG. 18A, timing diagram 1800 shows read cycles 1802 thatcorrespond with read logic of systolic array 1600. The read logic of thesystolic array 1600 reads the input that will be fed to the array.Systolic cycles 1804 correspond with how those inputs are processed ineach stage of the array. Write cycles 1806 correspond to output logicthat writes the output to specified destination locations. Inputs readin the cycle 0 of the read cycles 1802 are processed by the systolicarray in cycles 0-7 of the systolic cycles 1804. The inputs read incycle 1 of the read cycles 1802 are processed in cycles 1-8 of thesystolic cycles 1804. Processing that begins in cycle 0 of the systoliccycles 1804 are output in cycle “N” of the write cycles 1806. In oneembodiment, the value of N may be related to the depth of the systolicarray. Processing that begins in cycle 1 of the systolic cycles 1804 areprocessed in cycles 1-8 and output in cycle N+1 of the write cycles1806. Due to the pipelined nature of the array, the computations thatwill result in outputs at cycle N and N+1 are performed in parallel bythe various pipelined stages (Stage 1-Stage 8) of the systolic array.

Cycles of the read cycles 1802 lead the systolic cycles 1804 by one ormore cycles. For example, cycle 0 of the read cycles 1802 may occurbefore cycle 0 of the systolic cycles 1804. In one embodiment, cycle 1of the read cycles 1802 may happen concurrently with cycle 0 of thesystolic cycles 1804. During cycle 0 of the systolic cycles 1804, stage1 of the systolic array calculates Src0+Scr1*Src2.0 based on input thatis read in cycle 0 of the read cycles. Each of elements 0-7 of Src1 aremultiplied in parallel with element 0 of Src2 and added to correspondingelements 0-7 of Src0. The result from Stage 1 is passed to Stage 2. Incycle 1 of the systolic cycles 1804, the Stage 2 accumulates the resultcomputed by Stage 1 in cycle 0 with the result of [Src1+1]*Src2.1, whereelement 1 of Src2 is multiplied by each element of [Src1+1]. Scr1remains with Stage 1, such that in cycle 1, Stage 1 computes [Src0+1]+Scr1*[Src2+1.0] with the next Src0 and Src2 inputs. In stage 1, each ofelements 0-7 of Scr1 are multiplied in parallel with element 0 of[Src2+1] and added to corresponding elements of [Src0+1]. Processingcontinues in this pattern for each stage and each cycle, with resultsbeing output from stage 8 beginning at cycle N of the write cycles 1806.

As shown in FIG. 18B, timing diagram 1850 shows that systolic array 1700of FIG. 17A-17B processes the first group of inputs read in cycle 0 ofthe read cycles 1852 are processed, beginning with cycle 0 of thesystolic cycles 1854, in the same way as the first four stages of theeight deep pipeline of systolic array 1600 of FIG. 16 . It will beunderstood that in FIG. 18B, the read cycles 1852 are not necessarilyshown to be aligned with their corresponding cycle in the systoliccycles 1854. The read logic of systolic array 1700 can read the firstgroup of inputs in the same manner as systolic array 1600. The firstfour inputs read in cycles 0 through 3 of the read cycles 1852 can beprocessed in a pipelined fashion by systolic array 1700. Output isproduced in the cycle labeled as “N” in the write cycles 1856. Thus, thelatency to first output at cycle N of systolic array 1700 is the same aswith systolic array 1700. However, the throughput of systolic array 1700is reduced, as there is a delay between output of Dst3 and Dst4, whichare written in cycle N+8 through N+11 of the write cycles 1856 due tothe feedback.

For systolic array 1700, feedback begins in cycle 4 of the systoliccycles 1854. Feedback occurs until cycle 7. Once the feedback begins incycle 4 of the systolic cycles 1854, only Scr1 inputs are read by theprocessing elements, as represented by the dotted line inputs to cycle4, 5, 6, and 7 of the systolic cycles 1854. The next group of src0 andsrc2 inputs will be read by the processing elements beginning in cycle 8of the systolic cycles 1854. The read logic can delay the read of Src0and Src2 inputs until those inputs are needed or may read those inputsin conjunction with Scr1 inputs. Once inputs are read, those inputs maybe buffered and re-used by the systolic array.

The advantages of a matrix multiplication accelerator with feedback(systolic array 1700) relative to systolic array 1600 can be summarizedas follows: Systolic array 1700 can compute a similar pipeline depth assystolic array 1600 using less hardware. Systolic array 1700 allows theuse of the same instructions as the systolic array 1600 allowingworkloads developed for the systolic array 1600 to be reused withsystolic array 1700. Systolic array 1700 consumes less power byutilizing fewer pipeline stages. Systolic array 1700 can operate atreduced bandwidth for reads and writes relative to systolic array 1600.Systolic array 1700 can be implemented with any number of stages,although it may be optimal better to use multiples of two, in order toenable features of the embodiments shown below. While the architectureof systolic array 1700 has reduced throughout, the same throughput assystolic array 1600 can be enabled by implementing multiple instances ofsystolic array 1700 in parallel.

Scalable Matrix Multiply Accelerator with Feedback Inputs

A second embodiment enables increased throughput through the use ofsimultaneous instructions execution using parallel units. Severalinstances or paths of the multiply accelerator are run in parallel.These instances can share Scr1 or they can have independent Scr1 inputs.Each path will have their own Src2 and Src0 inputs. These instances willhave their own src2 and src0 inputs. A version showing two paths with adepth of four stages is shown in FIG. 19 . Alternatively, a versionusing four paths of depth of two stages is shown in FIG. 20 .

FIG. 19 illustrates a two-path matrix multiply accelerator 1900 in whicheach path has a depth of 4 stages. The two-path matrix multiplyaccelerator 1900 includes input logic 1902A-1902B for Src0 inputs, inputbuffers 1911A-1911B to store data elements received from input logic1910A-1910B, and input buffers 1913A-1913B to store data elementsreceived from shared input logic 1912 for Scr1. Each stage includes apair of processing elements, which may operate in parallel. Stage oneincludes processing elements 1931A-1931B, stage two includes processingelements 1932A-1932B, stage three includes processing elements1933A-1933B, stage four includes processing elements 1934A-1934B.Hardware logic of each of the processing elements 1931A-1931B,1932A-1932B, 1931A-1933B, 1934A-1934B can be the same as or similar tothe hardware logic of processing elements (e.g., processing elements1611A-1611D) of systolic array 1600 or systolic array 1700, and may bemanufactured with the same process technology or a more advanced processtechnology. The processing elements of the two-path matrix multiplyaccelerator 1900 may also operate at a higher frequency relative toimplementations of systolic array 1600. The processing elements and maybe manufactured using more advanced process technology.

Feedback may be implemented using data selectors that are the same as orsimilar to data selectors 1704, 1724. Depending on the configuration ofthe read logic, input data can be pre-fetched into the input buffer inadvance, or read from registers or a cache within the two-path matrixmultiply accelerator 1900 one or more cycles before input into theprocessing elements 1931A-1931B. Processing elements 1934A-1934B ofstage four can feed back into the corresponding processing elements1931A-1931B stage one. Dynamic logical depth may be enabled in multiplesof four. After a configured number of logical stages, results may bewritten by output logic 1922A-1922B to a specified destination.

FIG. 20 illustrates a four-path matrix multiply accelerator 2000 inwhich each path has a depth of 2 stages. Four-path matrix multiplyaccelerator 2000 includes the same number of processing elements astwo-path matrix multiply accelerator 1900, with the processing elementsconfigured with twice as many paths, but each path is half as deep.Four-path matrix multiply accelerator 2000 includes input logic2002A-2002D for Src0, input buffers 2011A-211D to store input elementsread by input logic 2010A-2010D for Src2, and input buffers 2013A-2013Dto store input elements read by shared input logic 2012 for Scr1.Processing elements 2031A-2031B enable parallel processing for stage 1.Processing elements 2032A-2032B enable parallel processing for stage 2.Stage 2 of each path can feed back into stage 1 or write results viaoutput logic 2022A-2022D to a specified destination. Processing elements2031A-2031B, 2032A-2032B may include hardware logic similar to that ofprocessing elements 1931A-1931B, 1932A-1932B, 1931A-1933B, 1934A-1934Band can implement loopback functionality using similar hardware logic.

The advantages of a two-path matrix multiply accelerator 1900 or afour-path matrix multiply accelerator 2000 include scalability, softwarecompatibility, and throughput. The modular architecture of theseaccelerators enables more efficient scaling relative to an 8-deepsystolic array. Different configurations of a matrix multiplyaccelerator can be tailored for different product needs or use caseswithout redesign. Additionally, the same software model that is used isindependent of the hardware implementation. Algorithms designed for aninstruction intended to be executed by a systolic pipeline of eightstages can be used in an implementation using a Matrix Multiplyaccelerator of 4 stages. Hardware will use feedback to simulate apipeline of 8 stages in a way that is transparent to the software.Multiple paths can be used in a design requiring high DPAS instructionthroughput. Implementations with a greater number of paths can becoupled with higher bandwidth input logic and output logic. In oneembodiment, the two-path matrix multiply accelerator 1900 and afour-path matrix multiply accelerator 2000 are configured to bypassinputs with block sparsity at a greater efficiency and/or finergranularity than possible with an 8-deep systolic array.

Sparse Multiplications on the Scalable Matrix Multiply Accelerator

A third embodiment facilitates increased instruction throughput whenprocessing for data with irregular sparsity. Elements of Scr1 and Src2inputs can be individually selected via input multiplexer logic andprocessing can be performed using only non-zero values.

FIG. 21 illustrates a scalable sparse matrix multiply accelerator 2100using systolic arrays with feedback inputs. Scalable sparse matrixmultiply accelerator 2100 can include processing elements 2031A-2031D asin four-path matrix multiply accelerator 2000, or any other processingelements described herein. Processing elements 2031A-2021B at thebeginning of each path include input logic for Src0. Each stage of eachpath of scalable sparse matrix multiply accelerator 2100 can receive anyelement of an independent or shared Scr1 via input selectors2112A-2112D. Each stage of each path can also receive any element of aSrc2. Independent Src2 inputs are provided via separate input elementselectors (e.g., Src2A via input selector 2110A and input selector2111A, Src2B via input selector 2110B and input selector 2111B). Theseparate Src2 input enables the separate paths to compute differentinstructions. Separate output logic 2122A-2122B is present for each pathto enable output for the different instructions.

FIG. 22 illustrates Src2 inputs 2200A-2200B including sparse data. Inthe illustrated example, sparse Src2 inputs 2200A-2200B (Src2A input2200A [A0, A1, 0, A3, A4, A5, A6, 0], Src2B input 2200B [B0, 0, B2, B3,0, 0, 0, 0]) can processed on each path of a variant of scalable sparsematrix multiply accelerator 2100 using a common Scr1 input. Each path ofthe scalable sparse matrix multiply accelerator 2100 can receive aseparate own Src0 input.

The first step in the computation process is to read the first Src2element and rearrange the elements into groups of N elements each, whereN is the depth of the path on which the elements will be processed.Other implementations with different numbers of paths can have differentgroup sizes. For example, an accelerator based on four-path matrixmultiply accelerator 2000 would use groups of four data elements. Ifpossible, only non-zero data elements will be selected. For example,non-zero values of Src2A 2200A are rearranged into three groups: [A0,A1], [A3,A4],[A5,A6]. The non-zero values of Src2B 2200B are rearrangedas two groups: [B0,B2], [B3,0], with a padding of zero used to completethe second group. This rearrangement is used to allow the first elementof each group to be fed to the first stage of the path and the secondelement of each group to the second stage of the path. While scalablesparse matrix multiply accelerator 2100 does not require elements to begroups, grouping the elements reduces the number of elements thatpossibly are required to be fed to a stage.

In the second step of the computation process the groups are fed to thepaths. Instead of performing four passes to compute an instructionhaving a depth of eight (e.g., eight feedback passes, each one using twostages), only three feedback passes are required as two elements arezero and do not require processing. The nature of the feedback allowsthat pass to be bypassed, with the accumulator value being sent directlyto the output without consuming a computational stage. To maintain thecorrect functional computation, the correct Scr1 element is input to thestage for a given Src2 element to be computed. Thus, when processing thesecond group ([A3, A4]), the first stage reads Src1-3 and the secondstage reads Src1-4. When processing Src2B 2200B, only two groups([B0,B2], [B3,0]) computed. The two groups can be computed using twofeedback passes instead of four. In the first pass, Src1-0 and Src1-2are input to the first and second stages. In the second pass Src1-3 andany Scr1 element are input to the first and second stages respectively.

For the third embodiment, the depth of the path constrains the number ofzeroes that can be reduced. In a matrix multiply accelerator with twostages in its paths (e.g., scalable sparse matrix multiply accelerator2100) for inputs of eight elements only reductions of eight, six, four,and two zeros can be performed. In a matrix multiply accelerator withfour stages in its paths, only reductions of eight and four zeroes canbe performed. To enable a higher resolution of sparse reduction, afourth embodiment adds an output on each stage of the paths and allowseach stage to receive the Src0 input, as shown in FIG. 23 .

FIG. 23 shows a scalable sparse matrix multiply accelerator 2300 usingsystolic arrays with feedback inputs and outputs on each stage. Scalablesparse matrix multiply accelerator 2300 includes similar hardware logicas scalable sparse matrix multiply accelerator 2100, along withadditional input and output logic to enable Src0 elements to be providedto each stage of each path and to provide separate outputs for eachstage of each path. In addition to input selectors 2110A and 2111A toselect Src2A elements for the first path and input selectors 2110A and2111B to select Src2B input for the second path, an input splitter2303A-2303B is added for each path for Src0 input. Each input splitter230A-2302B can include a demultiplexer or similar hardware logic toenable Src0 input elements that are read by input logic 2302A-2302B tobe sent to each stage. Input selectors 2112A-2112D are also included toenable Scr1 input to be elected by each stage of each path. In additionto output logic 2122A-2122B from the second stage of each path(processing element 2331C-2331D), additional output logic 2322A-2322B isprovided to enable output from the first stage of each path(2331A-2331B). The processing elements 2331A-2331C may be otherwisesimilar to other processing elements described herein.

During operation, scalable sparse matrix multiply accelerator 2300 isconfigurable to accept groups of only one element. Two groups ([B0,B2],[B3,0]) are made for the non-zero elements on Src2 for the thirdembodiment (e.g., scalable sparse matrix multiply accelerator 2100),with the second group including a zero padding. The optimizations shownin FIG. 23 enable the groups to be formed as [B0,B2], [B3]. B0 and B2will be assigned to the first and second stage of a path (e.g., eitherof a first set including of processing element 2331A and processingelement 2331C or a second set including processing element 2331B andprocessing element 2331D). After the feedback, B3 will be assigned tothe first stage of that path. As the first stage of a path can provideoutput (e.g., via either output logic 2322A or 2322B), there is no needto consume the second stage of the path (either of processing element2331C or processing element 2331D). Moreover, the next Src2 inputaccepted for that path can start from the second stage, so a group oftwo elements will be assigned to the second and first stagerespectively. Src0 for processing the new Src2 input can be assigned tothe second stage of the path (e.g., via either output logic 2322A or2322B)

In addition to the hardware logic of scalable sparse matrix multiplyaccelerator 2100 illustrated in FIG. 21 and scalable sparse matrixmultiply accelerator 2300 illustrated FIG. 23 , some embodimentsadditionally include input and output hardware memory buffers. Inputmemory buffers can be used to store and have ready groups of Src0 andSrc2 inputs, which reduces the need for high bandwidth input logic. Theoutput buffer allows Dst outputs generated in a same cycle to besteadily written to memory at a slower rate, which reduces the need forhigh bandwidth output logic.

Additionally, some embodiments include a bypass for inputs in which allelements are zero. The bypass allows a direct write of Src0 as by outputlogic without passing through the systolic array. This bypass is used inconcert with a data dependency strategy to prevent read-after-write(RAW) risks among instructions can damage the integrity of the data.

FIG. 24 illustrates a method 2400 by which hardware logic at afunctional unit can execute an instruction to perform a systolic dotproduct with accumulate, according to an embodiment. Method 2400 can beperformed via hardware and/or firmware logic of a scalable sparse matrixmultiply accelerator as described herein. The hardware and/or firmwarelogic can receive non-zero source values and a calculation depth for aninstruction to be executed by a matrix operation accelerator of a GPGPU(2402). The non-zero source values can be non-zero values that aregrouped according to a pipeline depth for a path of the scalable sparsematrix multiply accelerator. The calculation depth can specify a numberof systolic layers to use to calculate the dot product for theinstruction. The logic also receives an accumulator value and store theinitial value to an accumulator (2404). The accumulator value may be azero value, an initial accumulator value, or a result from a previouspipeline stage. For a specified layer of calculation, the logic canevaluate a write enable mask to determine a set of enabled parallelprocessing channels (2406). The write enable mask can be used to disablecalculation of specific channels. The write enable mask can beconfigured based on a predicate mask supplied with the instruction to beexecuted.

For each enabled parallel processing channel, the logic can generate aset of products based on an elementwise multiply of source inputelements (2408). For example, for a four-element dot product, a fourelements of two sources are multiplied to generate the set of products.In each layer of the systolic pipeline, the same Src2 element value ismultiplied by multiple different Src1 values. The logic can thencalculate a sum of the set of products and add the sum to a value in theaccumulator (2410).

Where method 2400 is executed on a processing element at the lastcalculation layer (2411) the processing element can output thecalculated sum to a specified destination register (2414). Otherwise,the processing element can output its accumulator value to the nextlayer (2412). The next layer may be a next physical layer or a nextvirtual layer. Output to the next virtual layer includes providing afeedback value to a processing element at the first stage of theprocessing pipeline.

In one embodiment, the method 2400 of FIG. 24 can be performed byhardware logic configured based on the pseudocode shown in below.

Four Element Systolic Dot Product with Accumulate V = Src2.regnum; temp= Src0.Regnum; // Accumulated register input k = Src2.regnum.subregnum; for (i = 0; i < sdepth; i++) {   U = Src1.(Regnum + i);   Evaluate(WrEn);   for (n = 0; n < exec_size; n++) {    if (WrEn.chan[n])    temp.chan[n] = temp.chan[n] +    U.chan[n].0 * V.k.0+      U.chan[n].1 * V.k.1 +       U.chan[n].2 * V.k.2 +      U.chan[n].3 * V.k.3;  //chan[n].0 is a 0^(th) byte in the nthdword      }    }    k ++ }     Dst.regnum = temp; // Write to outputregister

In the pseudocode shown above, Src0, Scr1, and Src2 are registers thatstore operand data. A systolic depth is specified by sdepth. Executionsize corresponds with exec_size, and is specifies the number of parallelprocessing channels. The destination is specified by the Dst register.In the pseudocode, the identified registers reference to regnum andsubregnum fields. The regnum field provides the register number for theoperand. The subregnum field provides the sub-register number for theoperand. The subregnum field, together with the corresponding RegNumfield, provides a byte aligned address for the origin of the registerregion. For some instructions, this field provides bits [4:0] of thebyte address, while the RegNum field provides bits [12:5].

FIG. 25 illustrates a method 2500 of performing a matrix multiplyoperation using a sparse Src2 input matrix. Method 2500 can be performedvia hardware and/or firmware logic of a scalable sparse matrix multiplyaccelerator as described herein. Method 2500 specifies operations usingsparse data, such as sparse Src2 inputs 2200A-2200B of FIG. 22 . Method2500 can be implemented using scalable sparse matrix multiplyaccelerator 2100 of FIG. 21 and/or scalable sparse matrix multiplyaccelerator 2300 of FIG. 23 .

Method 2500 includes for the hardware and/or firmware logic to readmultiple data elements of a first matrix and a second matrix into memoryof a matrix multiply accelerator (2502). The logic can then detectnonzero values within the multiple data elements of the second matrix(2504). Detection can be performed using vector comparison logic withinthe matrix multiply accelerator. The logic can then group detectednon-zero values within the multiple data elements of the second matrixinto a group including one or more data elements (2506). The logic canthen provide data elements of the group to corresponding stages of aprocessing pipeline of the matrix multiply accelerator (2508). For apath with a two stage pipeline, the groups will include two Src2elements. The first element of the group will be provided to the firststage and the second element of the group will be provided to the secondstage. For scalable sparse matrix multiply accelerator 2100, zeropadding is used to pad out a group if needed. For scalable sparse matrixmultiply accelerator 2300, zero padding is not required.

The logic then provides the multiple data elements of the first matrixto corresponding stages of the processing pipeline (2510). The multipledata elements provided are those Scr1 elements that correspond withactive channels that will be computed for a pipeline stage. Any Scr1element can be provided if the element will be operated on using a Src2zero padding value. Processing elements at each active stage of theprocessing pipeline performs multiply and accumulate operations (2512).Under some circumstances, for example, where scalable sparse matrixmultiply accelerator 2300 is processing a single element group, not allstages of the pipeline are active for an instruction. If a stage is notactive for the instruction, the stage can still be used to performoperations for a different instruction. The logic can then output orfeedback an accumulated value from each active stage of the processingpipeline (2514). Output can be written to a destination register ormemory location when the last stage of processing for an instructioncompletes. Alternatively, an accumulated value can be sent to the nextpipeline stage. Outputting to the next pipeline stage may involve awriting feedback output to the first physical stage of the processingpipeline.

Additional Exemplary Computing Device

FIG. 26 is a block diagram of a computing device 2600 including agraphics processor 2604, according to an embodiment. Versions of thecomputing device 2600 may be or be included within a communicationdevice such as a set-top box (e.g., Internet-based cable televisionset-top boxes, etc.), global positioning system (GPS)-based devices,etc. The computing device 2600 may also be or be included within mobilecomputing devices such as cellular phones, smartphones, personal digitalassistants (PDAs), tablet computers, laptop computers, e-readers, smarttelevisions, television platforms, wearable devices (e.g., glasses,watches, bracelets, smartcards, jewelry, clothing items, etc.), mediaplayers, etc. For example, in one embodiment, the computing device 2600includes a mobile computing device employing an integrated circuit(“IC”), such as system on a chip (“SoC” or “SOC”), integrating varioushardware and/or software components of computing device 2600 on a singlechip. The computing device 2600 can be a computing device such as thedata processing system 100 as in of FIG. 1 .

The computing device 2600 includes a graphics processor 2604. Thegraphics processor 2604 represents any graphics processor describedherein. In one embodiment, the graphics processor 2604 includes a cache2614, which can be a single cache or divided into multiple segments ofcache memory, including but not limited to any number of L1, L2, L3, orL4 caches, render caches, depth caches, sampler caches, and/or shaderunit caches. In one embodiment the cache 2614 may be a last level cachethat is shared with the application processor 2606.

In one embodiment the graphics processor 2604 includes a graphicsmicrocontroller that implements control and scheduling logic for thegraphics processor. The control and scheduling logic can be firmwareexecuted by the graphics microcontroller 2615. The firmware may beloaded at boot by the graphics driver logic 2622. The firmware may alsobe programmed to an electronically erasable programmable read onlymemory or loaded from a flash memory device within the graphicsmicrocontroller 2615. The firmware may enable a GPU OS 2616 thatincludes device management/driver logic 2617, 2618, and a scheduler2619. The GPU OS 2616 may also include a graphics memory manager 2620that can supplement or replace the graphics memory manager 2621 withinthe graphics driver logic 2622.

The graphics processor 2604 also includes a GPGPU engine 2644 thatincludes one or more graphics engine(s), graphics processor cores, andother graphics execution resources as described herein. Such graphicsexecution resources can be presented in the forms including but notlimited to execution units, shader engines, fragment processors, vertexprocessors, streaming multiprocessors, graphics processor clusters, orany collection of computing resources suitable for the processing ofgraphics resources or image resources, or performing general purposecomputational operations in a heterogeneous processor. The processingresources of the GPGPU engine 2644 can be included within multiple tilesof hardware logic connected to a substrate, as illustrated in FIG.11B-11D, The GPGPU engine 2644 can include GPU tiles 2645 that includegraphics processing and execution resources, caches, samplers, etc. TheGPU tiles 2645 may also include local volatile memory or can be coupledwith one or more memory tiles, for example, as shown in FIG. 3B-3C.

The GPGPU engine 2644 can also include and one or more special tiles2646 that include, for example, a non-volatile memory tile 2656, anetwork processor file 2657, and/or a general-purpose compute tile 2658.The GPGPU engine 2644 also includes a matrix multiply accelerator 2660.The general-purpose compute tile 2658 may also include logic toaccelerate matrix multiplication operations. The non-volatile memorytile 2656 can include non-volatile memory cells and controller logic.The controller logic of the non-volatile memory tile 2656 may be managedby one of device management/driver logic 2617, 2618. The networkprocessor tile 2657 can include network processing resources that arecoupled to a physical interface within the input/output (I/O) sources2610 of the computing device 2600. The network processor tile 2657 maybe managed by one or more of device management/driver logic 2617, 2618.

The matrix multiply accelerator 2660 is a modular scalable sparse matrixmultiply accelerator as described herein. The matrix multiplyaccelerator 2660 can includes multiple processing paths, with eachprocessing path including multiple pipeline stages. Each processing pathcan execute a separate instruction. In various embodiments, the matrixmultiply accelerator 2660 can have architectural features of any one ofmore of the matrix multiply accelerators described herein. For example,in one embodiment, the matrix multiply accelerator 2660 is a four-deepsystolic array 1700 with a feedback loop that is configurable to operatewith a multiple of four number of logical stages (e.g., four, eight,twelve, sixteen, etc.). In one embodiment the matrix multiplyaccelerator 2660 includes one or more instances of a two-path matrixmultiply accelerator 1900 with a four stage pipeline or a four-pathmatrix multiply accelerator 2000 with a two stage pipeline. In oneembodiment the matrix multiply accelerator 2660 includes processingelements configured as the scalable sparse matrix multiply accelerator2100 or the scalable sparse matrix multiply accelerator 2300. The matrixmultiply accelerator 2660 can be configured to operate only on non-zerovalues of at least a Src2 input, and may also bypass operations wherezero values are present in the Src1 input. Operations on entiresubmatrices can be bypassed where block sparsity is present. The matrixmultiply accelerator 2660 can also include any logic based on anycombination of these embodiments.

As illustrated, in one embodiment, and in addition to the graphicsprocessor 2604, the computing device 2600 may further include any numberand type of hardware components and/or software components, including,but not limited to an application processor 2606, memory 2608, andinput/output (I/O) sources 2610. The application processor 2606 caninteract with a hardware graphics pipeline, as illustrated withreference to FIG. 3A, to share graphics pipeline functionality.Processed data is stored in a buffer in the hardware graphics pipelineand state information is stored in memory 2608. The resulting data canbe transferred to a display controller for output via a display device,such as the display device 318 of FIG. 3A. The display device may be ofvarious types, such as Cathode Ray Tube (CRT), Thin Film Transistor(TFT), Liquid Crystal Display (LCD), Organic Light Emitting Diode (OLED)array, etc., and may be configured to display information to a user viaa graphical user interface.

The application processor 2606 can include one or processors, such asprocessor(s) 102 of FIG. 1 and may be the central processing unit (CPU)that is used at least in part to execute an operating system (OS) 2602for the computing device 2600. The OS 2602 can serve as an interfacebetween hardware and/or physical resources of the computing device 2600and one or more users. The OS 2602 can include driver logic for varioushardware devices in the computing device 2600. The driver logic caninclude graphics driver logic 2622, which can include the user modegraphics driver 1026 and/or kernel mode graphics driver 1029 of FIG. 10. The graphics driver logic can include a graphics memory manager 2621to manage a virtual memory address space for the graphics processor2604.

It is contemplated that in some embodiments the graphics processor 2604may exist as part of the application processor 2606 (such as part of aphysical CPU package) in which case, at least a portion of the memory2608 may be shared by the application processor 2606 and graphicsprocessor 2604, although at least a portion of the memory 2608 may beexclusive to the graphics processor 2604, or the graphics processor 2604may have a separate store of memory. The memory 2608 may comprise apre-allocated region of a buffer (e.g., framebuffer); however, it shouldbe understood by one of ordinary skill in the art that the embodimentsare not so limited, and that any memory accessible to the lower graphicspipeline may be used. The memory 2608 may include various forms ofrandom-access memory (RAM) (e.g., SDRAM, SRAM, etc.) comprising anapplication that makes use of the graphics processor 2604 to render adesktop or 3D graphics scene. A memory controller hub, such as memorycontroller 116 of FIG. 1 , may access data in the memory 2608 andforward it to graphics processor 2604 for graphics pipeline processing.The memory 2608 may be made available to other components within thecomputing device 2600. For example, any data (e.g., input graphics data)received from various I/O sources 2610 of the computing device 2600 canbe temporarily queued into memory 2608 prior to their being operatedupon by one or more processor(s) (e.g., application processor 2606) inthe implementation of a software program or application. Similarly, datathat a software program determines should be sent from the computingdevice 2600 to an outside entity through one of the computing systeminterfaces, or stored into an internal storage element, is oftentemporarily queued in memory 2608 prior to its being transmitted orstored.

The I/O sources can include devices such as touchscreens, touch panels,touch pads, virtual or regular keyboards, virtual or regular mice,ports, connectors, network devices, or the like, and can attach via aplatform controller hub 130 as referenced in FIG. 1 . Additionally, theI/O sources 2610 may include one or more I/O devices that areimplemented for transferring data to and/or from the computing device2600 (e.g., a networking adapter); or, for a large-scale non-volatilestorage within the computing device 2600 (e.g., SSD/HDD). User inputdevices, including alphanumeric and other keys, may be used tocommunicate information and command selections to graphics processor2604. Another type of user input device is cursor control, such as amouse, a trackball, a touchscreen, a touchpad, or cursor direction keysto communicate direction information and command selections to GPU andto control cursor movement on the display device. Camera and microphonearrays of the computing device 2600 may be employed to observe gestures,record audio and video and to receive and transmit visual and audiocommands.

The I/O sources 2610 can include one or more network interfaces. Thenetwork interfaces may include associated network processing logicand/or be coupled with the network processor tile 2657. The one or morenetwork interface can provide access to a LAN, a wide area network(WAN), a metropolitan area network (MAN), a personal area network (PAN),Bluetooth, a cloud network, a cellular or mobile network (e.g., ³rdGeneration (3G), ⁴th Generation (4G), ⁵th Generation (5G), etc.), anintranet, the Internet, etc. Network interface(s) may include, forexample, a wireless network interface having one or more antenna(e).Network interface(s) may also include, for example, a wired networkinterface to communicate with remote devices via network cable, whichmay be, for example, an Ethernet cable, a coaxial cable, a fiber opticcable, a serial cable, or a parallel cable.

Network interface(s) may provide access to a LAN, for example, byconforming to IEEE 802.11 standards, and/or the wireless networkinterface may provide access to a personal area network, for example, byconforming to Bluetooth standards. Other wireless network interfacesand/or protocols, including previous and subsequent versions of thestandards, may also be supported. In addition to, or instead of,communication via the wireless LAN standards, network interface(s) mayprovide wireless communication using, for example, Time Division,Multiple Access (TDMA) protocols, Global Systems for MobileCommunications (GSM) protocols, Code Division, Multiple Access (CDMA)protocols, and/or any other type of wireless communications protocols.

It is to be appreciated that a lesser or more equipped system than theexample described above may be preferred for certain implementations.Therefore, the configuration of the computing device 2600 may vary fromimplementation to implementation depending upon numerous factors, suchas price constraints, performance requirements, technologicalimprovements, or other circumstances. Examples include (withoutlimitation) a mobile device, a personal digital assistant, a mobilecomputing device, a smartphone, a cellular telephone, a handset, aone-way pager, a two-way pager, a messaging device, a computer, apersonal computer (PC), a desktop computer, a laptop computer, anotebook computer, a handheld computer, a tablet computer, a server, aserver array or server farm, a web server, a network server, an Internetserver, a work station, a mini-computer, a main frame computer, asupercomputer, a network appliance, a web appliance, a distributedcomputing system, multiprocessor systems, processor-based systems,consumer electronics, programmable consumer electronics, television,digital television, set top box, wireless access point, base station,subscriber station, mobile subscriber center, radio network controller,router, hub, gateway, bridge, switch, machine, or combinations thereof.

Described herein is an accelerator device including a host interface, afabric interconnect coupled with the host interface, and one or morehardware tiles coupled with the fabric interconnect, the one or morehardware tiles including sparse matrix multiply acceleration hardwareincluding a systolic array with feedback inputs.

One embodiment provides for a parallel processor comprising a decodeunit to decode an instruction into a decoded instruction, where thedecoded instruction is an instruction to perform a parallel dot productoperation, and a pipelined systolic dot product unit. The pipelinedsystolic dot product unit is configured to execute the decodedinstruction via multiple pipeline stages of a systolic processingpipeline. During execution of the decoded instruction, a dot productcomputed at a first pipeline stage is configured to be selectablywritten via output hardware to a location selected from one of outputmemory and a second pipeline stage and a dot product computed at a thirdpipeline stage is configured to be selectably written via outputhardware to a location selected from one of the output memory and thefirst pipeline stage. In a further embodiment, the decoded instructionis associated with a first source operand and a second source operand,the first source operand is a reference to memory storing multiple dataelements of a first matrix, and the second operand is a reference tomemory storing multiple data elements of a second matrix.

One embodiment provides for an accelerator device comprising a hostinterface, a fabric interconnect coupled with the host interface, andone or more hardware tiles coupled with the fabric interconnect. The oneor more hardware tiles include sparse matrix multiply accelerationhardware including a modular systolic processing array with feedbackinputs. The modular systolic processing array include one or moreprocessing array modules having a first number of pipeline paths and thefirst number of pipeline paths have a second number of pipeline stages.A first pipeline stage is configurable to receive feedback output from afinal pipeline stage.

One embodiment provides for a method of performing a dot productoperation on a set of input matrices via a hardware matrix multiplyaccelerator having a multi-stage processing pipeline. The methodcomprises reading, via a first source operand, multiple data elements ofa first matrix into memory of the hardware matrix multiply accelerator,reading, via a second source operand, multiple data elements of a secondmatrix into the memory of the hardware matrix multiply accelerator,detecting non-zero values within the multiple data elements of thesecond matrix, grouping the non-zero values within the multiple dataelements of the second matrix into a group including one or more dataelements, where a number of data elements of the group corresponds witha number of stages in the multi-stage processing pipeline of thehardware matrix multiply accelerator, providing a data element of thegroup to a corresponding stage of the processing pipeline bybroadcasting the data element to multiple channels of a processingelement of the corresponding stage, multiplying, a provided data elementof the group with multiple data elements of the first matrix to generatea set of products, summing the set of products and accumulating a sum ofthe set of products with an accumulator value, and writing theaccumulator value to a next stage of the processing pipeline. In afurther embodiment, writing the accumulator value to the next stage ofthe processing pipeline includes writing a pipeline feedback value to afirst stage of the processing pipeline. Additionally, detecting thenon-zero values within the multiple data elements of the second matrixcan include detecting the non-zero values within the memory of thehardware matrix multiply accelerator.

Those skilled in the art will appreciate from the foregoing descriptionthat the broad techniques of the embodiments can be implemented in avariety of forms. Therefore, while the embodiments have been describedin connection with particular examples thereof, the true scope of theembodiments should not be so limited since other modifications willbecome apparent to the skilled practitioner upon a study of thedrawings, specification, and following claims.

What is claimed is:
 1. A graphics processor comprising: a hostinterface; a plurality of processing clusters coupled with the hostinterface, each processing cluster of the plurality of processingclusters comprising a plurality of multiprocessors, the plurality ofmultiprocessors interconnected via a data interconnect, and eachmultiprocessor of the plurality of multiprocessors comprising sparsematrix multiply acceleration hardware including: a systolic processingarray with feedback inputs, the systolic processing array comprisingmultiple processing array modules, the multiple processing array modulesincluding a processing array module having a first number of pipelinepaths, the first number of pipeline paths having a second number ofpipeline stages, wherein a first pipeline stage is configurable toreceive feedback output from a final pipeline stage and the processingarray module includes pipeline paths configured with shared circuitry toread data elements associated with a first source input and separatecircuitry to read data elements associated with a second source input.2. The graphics processor as in claim 1, wherein the processing arraymodule includes pipeline paths configured with first circuitry to readdata elements associated with a first source input and second circuitryto read data elements associated with a second source input.
 3. Thegraphics processor as in claim 2, wherein the processing array moduleinclude third circuitry configured to detect non-zero data elements inthe second source input and selectively perform dot product operationsbased on the non-zero data elements of the second source input and dataelements of the first source input that correspond with the non-zerodata elements of the second input.
 4. The graphics processor as in claim3, wherein the processing array module include a pipeline path includingseparate output hardware for each pipeline stage.
 5. The graphicsprocessor as in claim 4, wherein the processing array module include afirst pipeline path configurable to execute a first dot productinstruction having a first set of inputs and a second pipeline pathconfigurable to execute a second dot product instruction having a secondset of inputs.
 6. The graphics processor as in claim 4, the pipelinepath including first output hardware configured to selectably writeoutput of the first pipeline stage to a location selected from one ofoutput memory and a second pipeline stage.
 7. The graphics processor asin claim 6, the pipeline path including second output hardwareconfigured to selectably write output of the of the final pipeline stagea location selected from one of output memory and the first pipelinestage.
 8. The graphics processor as in claim 7, wherein the secondpipeline stage is the final pipeline stage.
 9. A method comprising:receiving non-zero source values and a calculation depth for aninstruction to be executed by a matrix accelerator of a general-purposegraphics processor, the calculation depth to specify a number ofpipeline stages to use to calculate a dot product in response to theinstruction; evaluating a write enable mask to determine a set ofenabled parallel processing channels; generating a set of products basedon an elementwise multiply of source input elements; calculating a sumof the set of products and adding the sum to a value in an accumulator;at a processing element at a non-final calculation layer of the matrixaccelerator, outputting the accumulator value to a next layer of thematrix accelerator; and at a processing element at a final calculationlayer of the matrix accelerator, outputting the calculated sum to aspecified destination register.
 10. The method of claim 9, furthercomprising: receiving an initial accumulator value along with thenon-zero source values and the calculation depth; and storing theinitial value to the accumulator before adding the sum to the value inthe accumulator.
 11. The method of claim 9, wherein outputting theaccumulator value to a next layer of the matrix accelerator includesproviding a feedback value to a processing element at an initial stageof the processing pipeline.
 12. The method of claim 9, furthercomprising configuring the write enable mask based on a predicate maskreceived with the instruction.
 13. A data processing system comprising:a host processor; and a graphics processor coupled with the hostprocessor vis a host interface, the graphics processor comprising aplurality of processing clusters, each processing cluster of theplurality of processing clusters comprising a plurality ofmultiprocessors, the plurality of multiprocessors interconnected via adata interconnect, and each multiprocessor of the plurality ofmultiprocessors comprising sparse matrix multiply acceleration hardwareincluding: a systolic processing array with feedback inputs, thesystolic processing array comprising multiple processing array modules,the multiple processing array modules including a processing arraymodule having a first number of pipeline paths, the first number ofpipeline paths having a second number of pipeline stages, wherein afirst pipeline stage is configurable to receive feedback output from afinal pipeline stage and the processing array module includes pipelinepaths configured with shared circuitry to read data elements associatedwith a first source input and separate circuitry to read data elementsassociated with a second source input.
 14. The data processing system asin claim 13, wherein the processing array module includes pipeline pathsconfigured with first circuitry to read data elements associated with afirst source input and second circuitry to read data elements associatedwith a second source input.
 15. The data processing system as in claim14, wherein the processing array module include third circuitryconfigured to detect non-zero data elements in the second source inputand selectively perform dot product operations based on the non-zerodata elements of the second source input and data elements of the firstsource input that correspond with the non-zero data elements of thesecond input.
 16. The data processing system as in claim 15, wherein theprocessing array module include a pipeline path including separateoutput hardware for each pipeline stage.
 17. The data processing systemas in claim 16, wherein the processing array module include a firstpipeline path configurable to execute a first dot product instructionhaving a first set of inputs and a second pipeline path configurable toexecute a second dot product instruction having a second set of inputs.18. The data processing system as in claim 16, the pipeline pathincluding first output hardware configured to selectably write output ofthe first pipeline stage to a location selected from one of outputmemory and a second pipeline stage.
 19. The data processing system as inclaim 18, the pipeline path including second output hardware configuredto selectably write output of the of the final pipeline stage a locationselected from one of output memory and the first pipeline stage.
 20. Thedata processing system as in claim 19, wherein the second pipeline stageis the final pipeline stage.